It's not necessarily always good for the bots either. They can be exploited and tricked as well.
Is the money really "locked up"? No money actually enters these systems; whenever someone buys a token with money, there was someone else selling that token for money, and the money went from the buyer to the seller, who is free to do anything with that money.
anyway, yes there is money locked in the lending platforms. most of it is used as collateral, which is locked when borrowed against. the reserve ratios are high (60-80%), so unlike a regular bank, no money is "printed" when lent.
"real money" does enter these systems. people spend resources to acquire real money which is subsequently traded then locked into these platforms. also, while a lot of ethereum tokens are simply minted with no real backing, some are mined (even erc20), which again people dedicate finite resources to