I think it makes it much harder for them to bid slam, and maybe we get a good lead sometimes, and maybe partner bids 4S sometimes and pushes them to 5H or it's a good save (though sometimes this will be 800, I'll take my chances). Admittedly if we pass partner will overcall 1S on those hands then we can preempt, but it seems more effective if we bid first since RHO won't have had a chance to bid yet. Usually I would pass with this hand btw, 1S doesn't have huge gains but I don't view it as very risky either. I would be more likely to do it vs weak opps because I think the biggest downside of 1S is that the subsequent bidding should help them play the hand (because partners bidding will be honest), but usually against bad players it will make them misplay the hand anyways (HE OPENED! HE MUST HAVE THE HONORS!).