Yea there's plenty of benefits using a truncation library (we're currently using react-lines-ellipsis) over just css truncation. More control over how the truncation happens, callback so you can do more stuff on the condition that truncation has occurred, multi-line truncation as you mentioned, etc etc.

I get the feeling that most of the time when people are complaining about unnecessary libraries they simply haven't personally run into the problem that the library solves yet.