Because the result is that small landlords who can't deal with the fixed costs hassles simply sell out and consolidate into larger ones with more clout with politicians to weaken renter rights and legal resources to fight pesky tenants whom they simply don't want, or create shared blacklist databases like has been done in New York. If you're going to gird up for class warfare, realize that tenants are probably going to lose as long as zoning restricts your options