Didn't realize anime was sold this way. Although with streaming options there really is no need to buy anime anymore other than really obscure licensed stuff. RIP the days of $30 VHS tapes that contained 3 - 4 episodes
Anime is sold via all sorts of streaming sites, though the most obvious and accessible are stores like this, iTunes, and PSN. Basically their whole idea is that you can buy anime and then stream it in high quality without ads or commercials, or in the case of PSN you can download DRM protected files for the anime which can only be viewed on Playstation devices. Its fairly common practice.
I'd argue that you're quite a ways off however regarding streaming/anime sales. Most streaming options that people use are actually illegally hosting anime, meaning that the creators see less of a profit because so many people are watching via said websites. Said websites also typically feature anime at a much lower resolution quality or generally have issues of some kind. Much older titles such as that in the mid 2000s or earlier might even have poor or strange fansubs on such sites. Fansubbing quality varies, and generally nowadays its either much better or intentionally bad, but in general most streaming sites that people use aren't very good. Crunchyroll is a decent official one, as is Daisuke and even Hulu, but they are also somewhat unreliable service wise, or maybe they have commercials and such unless you pay a subscription, and some people can't even bring themselves to do that.
There's much good reason to buy and purchase anime, and in your instance with obscure shows its actually quite the opposite; many obscure anime are only available in the West via random illegal/questionably legal streaming sites or torrenting sites, and purchasing such works is near impossible since they're either unlicensed, old and no longer sold, or both. A particular favorite anime of mine, Renkin Sankyuu Magical Pokaan, suffers from this for instance. Oftentimes streaming sites are better than purchases for obscure works, while for bigger name titles for the best experience its honestly best to just buy blurays.
You get a permanent physical copy of a show in its highest quality at levels that streaming can't even attain, with no ads and no need for a continuous paid subscription or shoddy streaming service. Plus it helps support the anime industry.