I read Sega actually changed those rates to adapt to a new japanese law regarding gacha-style games. As long as a similar law doesn't force gumi to do the same, they are pretty much free to leave them unchanged.
Still, that would mean a lot of people would give them the middle finger, so it wouldn't be a wise decision.
Also, as long as v2 goes, increased rates do help, but even with the pick-up system (a set of ssr and sr are more likely to drop, over the rest of ssr and sr) you are pulling from a bigger poll of ssr and sr, so lbing a character is pretty difficult, and you actually need to Lb them in v2.
Then again, power creep and a higher rate means waiting makes a lot of sense if you already ave all the rings you need.
