It's not just about cashing in outright. I don't know Mukam's situation exactly, but it's 100% true that a lot of top programs are basically cutting Rev Share substantially to depth players, in order to ensure that their starting caliber players are competively compensated such that they don't get poached by other peer programs.
It's been widely reported, for example, that ND is in the game of giving large (six figure) signing bonuses to high school recruits to get to them to South Bend. However, beyond that first payment, their future Rev Share is based on playing time / production. Therefore, if you got paid $200,000 as a freshman, and didn't play, ND might be re-negotiating you down to $20,000-$50,000 in year two, saying that they'll re-negotiate heading into year three and re-evaluate your worth depending on your value to the program at that point.
If you go from making $200,000 to making $50,000 and you don't see a reasonable path towards you getting back to that $200,000 (or more), you might just look around... If some mid-tier program says "you're making $50,000? We'll pay you $100,000 to transfer and guarantee playing, giving you the opportunity to be productive and make even more next year." That's enticing for a lot of guys.
If you don't think that's happening all over the country, I don't know what to tell you. Lots of kids are transferring with that in mind.