Why would they make a combo steroid and antibiotic ointment for eyes?

Guessers . Stupid combo. The antibacterial used in these combination drugs is often tobramycin, which is not a first line antibiotic for eye infections.Tobramycin main action is towards gram negative bacteria. Eye infections and the ones responsible for blindness are gram positive. Steroids decrease the immune system. All my professors are against them. They make patient feel better. I don't prescribe.
Why not? Sometimes you need both- the antibiotic to kill the bugs, and a steroid to quiet the eye down.