You buy a regular 9mm from the store in real life, and it will have Iron Sights.
Precision rifles have been sold without iron sights for decades now. Not all but many. People using different optics on handguns is newer but has been around a lot that some handguns are sold without iron sights as the expectation that somebody will be mounting a more modern sighting system on the gun is more and more likely every year.
A decent number of people also seem to prefer buying AR-15s with a completely flat railed top without iron sights, and occasionally adding detachable rail mounted irons back on them.
In a game like this I think having even iron sights be their own thing is
okay. There needs to be more thought put into things being taken from the player as nobody is gonna bother pinching specifically the iron sights from a gun and nothing else. Item stealing should probably be limited to inventory items, clothing items and to threaten the player's ability to fight back... maybe their entire gun, but that seems unfair with how the game works so maybe just stealing their magazines or something would be a decent option. Ammo is valuable, if it's loaded into a mag it's conveniently housed and you're disarming the victim at the same time. While their gun is probably really shitty and heavy anyway.
It's a system that is more of a proof of concept anyway. I think having more guns is a better way to solve the issue. Most
should come with irons, I agree. But then some meme operator's tricked out gat while very valuable may not even have any backup irons. It is also worth remembering that this setting is arbitrarily sci-fi, so if people are moving away from irons IRL, the move will have been more substantial years into the future.