There are a lot of compelling and expedient reasons why iOS is the way it is. Apple isn't the only player on the market, and they aren't misleading or a monopolist like IBM was in the 80s or Microsoft in the 90s.
As for why can't you do on iOS what you can do on your Mac... Apple doesn't want the types of problems that android has.
You're right this is not like Microsoft in the 1990s. It's significantly worse than that. Microsoft, for all their faults, constantly championed developers on their platform. Just think of that Steve Balmer "Developers! Developers! Developers!" video.
Apple, on the other hand, consistently treats developers on its platform with nothing but disdain.
Worse -- For developers. Apple's customers are users.
Users benefit from a secure system, mostly safe applications and consistent UI.
The consequence of Microsoft's fuck-the-user, go developer philosophy has been over a decade a pain for the users. That's why Dell and HP are giving away PCs under cost while giving up share, while Apple is growing and making a killing.
There are a lot of compelling and expedient reasons why iOS is the way it is. Apple isn't the only player on the market, and they aren't misleading or a monopolist like IBM was in the 80s or Microsoft in the 90s.
As for why can't you do on iOS what you can do on your Mac... Apple doesn't want the types of problems that android has.