I only flat benched bodybuilding style the first 2 months of my training, because it hurt my shoulders.
For 5 years, my only straight bar benching was done incline, or flat close grip.
After those 5 years, I was shown how to do a powerlifting style flat bench, and after 2 months I had worked up to the same poundage I did on the incline.(which was very respectable)
A few years later, of course, I could do more, both in the gym as in competition.
From a bodybuilding standpoint, it’s useful, but definately not necessary.
From a powerlifting standpoint, it’s definately necessary(duh), but can be substituted for some periods of time, to give your body a break.
NOTE : I’ve never had a shoulder injury(outside of a broken collarbone due to a fall)due to benching or any other kind of press.
Something to consider.