There has been recent controversy over the reason Kyoryuger has no Yellow.
So...sexism.
Sentai is mostly aimed at kids, with older women and male fans as secondary demographics. Same for Kamen Rider. That's why you get a ton of toys (for kids), collector's merchandise (for fans), and male models/drama (for the women) in the shows.
Here's a good breakdown from Lynxara of Henshin Justice:
Although 80's Sentai had more graphic stuff in them (more blood and gore), the stories were a lot more like what you saw with Kyoryuger; stuff happening with no explanation and more nonsensical. The idea that Sentai stories should be more realistic and make more sense is a recent trend.
Takahito Ohmori said:“This is actually not the first time a team is without a Yellow member, J.A.K.Q, Battle Fever J and Dengeki Sentai Changeman never had a Yellow member. When it was decided that the Kyoryuger’s would be required to defeat a dinosaur in order to be able to transform, we wanted the characters to be absurdly strong. In order to show this, we chose to have more male characters over female characters. Seeing how modern Yellows have been female, we couldn’t have a male Yellow. If the Yellow was a male, the kids would probably think is feminine and we wanted to avoid that.”
So...sexism.
Sentai is really aimed toward males in their early teens, isn't it? I always though that 80's Sentai were more mature. I wonder if it's just Nostalgia talking. I really should look for a Kamen Rider to watch.
Sentai is mostly aimed at kids, with older women and male fans as secondary demographics. Same for Kamen Rider. That's why you get a ton of toys (for kids), collector's merchandise (for fans), and male models/drama (for the women) in the shows.
Here's a good breakdown from Lynxara of Henshin Justice:
Kids
This is Rider’s most important and largest demographic, generally comprised of viewers 12 and under. Generally, a Rider show’s ratings with Kids will be much higher than its standard rating, since most of the audience is children. While the lowest-rated completed Rider series to date has a standard rating of 6.2% (Kiva), the lowest average rating with Kids the Heisei Rider series has ever pulled is 11.6% (during Kiva). That rating indicates that Heisei Rider at its least successful is still being watched regularly by about 1 in 10 Japanese children. An extremely successful Rider show like Faiz can pull a Kids demographic rating as high as 19.5%, effectively drawing in 1 in 5 kids.
M1 and F1
These demographic groups track viewers aged 20 to 35, with M1 indicating men in this age range and F1 indicating women. M1 and F1 together probably constitute Rider’s second-most-important demographic block. F1 viewers will tend to be mothers of young children who watch the shows as part of family time on Sunday mornings. M1 can include fanboy dads, as well as single viewers who are just enthusiastic fans of superheroes. M1 is very likely to buy lots of merchandise and high-end collector toys (like the S.H. FiguArts and S.I.C. lines). M1 is a more fickle group than F1, though, and quickly tunes out of shows it finds uninteresting or too childish. A typical M1 rating for Rider ranges from about 3% to 10%, while a typical F1 rating ranges from 3% to 8%. It’s worth noting that F1 tunes into Rider much more consistently than M1 does. That is, F1 is more likely to watch Rider every year, regardless of changes made to staff, cast, or concept.
M2 and F2
These demographic groups track viewers aged 36 to 49. It has some similarities to M1 and F1, since viewers at the young end of this range may still be parents with young children in the house (or are still single, and can afford to buy lots of collector goods). Overall, viewership in M2 and F2 is lower, since viewers at the high end of the age range tend to be at a point in life where Sunday morning superheroes aren’t especially interesting. Viewership among M2 tends to range from about 0.5% to 8%. As with teens, you typically only see the high end of the range with shows that are big hits. Among F2, the range is about 2% to 7%. For the same reasons that F1 ratings tend to be more consistent than M1, F2 also tends to watch Rider more consistently than M2. F1 and F2 together would constitute the “housewives” demographic that has reportedly influenced Rider’s production for quite some time.
Teens
You might think Teens would also be an important demographic for Rider shows, but this is often not the case. The Teens demographic indicates viewers in the 13 to 19 range: middle school students, high school students, and young adults either beginning their careers or entering college. The early years in this range are a busy and stressful time in a Japanese person’s life, and as a result, younger Teen viewers don’t have a lot of spare time. Viewers in the older end of the range have more spare time, but lots of entertainment competes for their attention. They may tune into Rider and buy merchandise, but aren’t consistent about doing so. A typical Teen rating for a Rider show can range from about .5% to about as high as 8%. You typically only see the higher end of the range with hit shows.
Although 80's Sentai had more graphic stuff in them (more blood and gore), the stories were a lot more like what you saw with Kyoryuger; stuff happening with no explanation and more nonsensical. The idea that Sentai stories should be more realistic and make more sense is a recent trend.