Depends on the application - for my truck (sometimes daily driven, used to pull horse/car trailer) I just like keeping track of engine wear so I'm not surprised if it spins a bearing and leaves my wife stranded on the side of the road with a trailer full or horses. It's also helped me feel good about increasing my oil change intervals
In my DD mini that I bought with high miles, I use it to monitor engine health (the N18 motor is known for oiling problems)
In my Morgan after I rebuilt the engine I monitored heavy metals for break and and continue to monitor them for tappet/ring wear. I've also dealt with a leaking fuel pump which would increase the flashpoint of the oil so would be caught that way
On my BMW race car I kept a close track of piston ring and bearing wear, and when analysis results started looking suspect I rebuild the engine - revealing some good cylinder scoring and a very worn main bearing (rebuilding it now).
