"Why should the government tell me I need this many exits, or that I need a wheelchair ramp if no-one needs it?"
"Because you're too short-sighted to see how important those things are. The government is watching out for you and those unfortunate enough to know you."
1. Fire sprinklers were added to the IRC and IBC due to their ability to prevent fires (surprise!), in light of the fact that costs have come down significantly, and they can now make them look "not ugly".
Fires aren't just going to damage your building, they'll damage the stuff you don't own as well.
2. The number and placement of fire exits is usually based on the distance one has to travel from any given occupied space, and the occupancy of the building. This distance is determined based on real numbers like how far you are likely to get before smoke inhalation kills you.
Letting the probably non-existent free market sort this out by "the people who didn't die" learning to only frequent places that have sufficient fire exits seems like a bad strategy.
3. You probably don't remember the wonderful days before the ADA, when there weren't many wheelchair ramps, and people with wheelchairs were basically told to "suck it" everywhere they went (including, in some cases, government buildings).
Fire exits are required to make sure people can exit a burning building within 3-7 minutes (varies by jurisdiction). This is based on an unfortunate history of tragedies involving people dying in fires, in which it was discovered that people who did not manage to escape in the first few minutes usually succumbed to the smoke.
The rest? Most of it sounds like a combination of people wanting to believe nothing bad can ever happen to them and the nanny state wanting to keep itself employed.