$100 fee is really high, it's way bigger than Ethereum's network fee, so what's the reason for that? Must be because of some specific DeFi mechanisms, right? But regardless, some people would still be using DeFi right now, if they put thousands of dollars, and expect quick returns, $100 isn't a big fee for them. Also, there's no adoption of DeFi in real world anyway, right now it's just a toy for crypto enthusiast to make high risk investments. No one in real life is putting their money into DeFi instead of traditional funds.
In general, the trend of investing in DeFi projects is attracting a lot of big investors, so the $100 fee is probably a small thing for them.
Also, those coins are very easy to increase in price and can be x2 or x3 in just a short time so that is enough for them to make a huge profit. I hope that Ethereum 2.0 will fix this problem soon as the high gas fees also make me feel very uncomfortable when trading.