Two seasons is the limit for Nick and Disney to determine whether or not the show has traction. That isn't how CartoonNetwork functions, but it's how the other two do. And for Disney, it's not even dealt that way all the time. Star Vs has been renewed for four seasons, they wanted to have three seasons for Gravity Falls but Alex said no, Pickle and Peanut is getting three seasons.
Nick and Disney also make tons of live-action shows because they're cheap but when CN did that, everyone flipped out, so it's a good thing they don't follow what everyone else does.
CN just six months ago was able to get 1.5 to 2 mil in ratings for their best shows and now they've dwindled to under a mil consistently across the board. Even if they're getting good numbers in streams, unless they plan on shutting down their channel altogether, it's not a good idea to sacrifice their channels ratings in favor of their stream. It's only going to further push them not giving a shit about their schedule and airing TTG + Diary of a Wimpy Kid non-stop. They've already gotten the worse they can by having a Gumball only marathon on Mothers Day simply because it's their second most popular show. If TTG had a mom character, they wouldn't even fucking bother.
They could have had Regular Show episodes with moms, Adventure Time special with Marceline's mom, Clarence episodes that focus on the mom, SU episodes about Rose. Instead, just lazily air Gumball all day. They really don't seem to give a shit about their channel and only focus on streams and app games when there's no real reason for them to not put effort in both.