Can someone explain to me why Corps are buying Bitcoin, XRP, and Ethereum?

Recently i’ve heard discussion of big Mega-Corporations buying up Bitcoin, Ethereum, and XRP in large quantities. I watched a couple of videos and read some articles but i’m still at a complete lost. What i’ve really gotten out of the videos/articles is that they’re tryin to make their own reserved currency in the sense of blockchains/tokens and really cut out the middle man in transferring fees and other fees that come along with dealing with Crypto currencies. But the problem is i thought all these crypto currencies only have a limited amount of supplies; like bitcoin for instance having like 21~ million and only like a couple mill to be mined; Any explanation would be great!