I remember back in the day working in companies of 15-40 people. There'd be ONE server. That ran everything you needed -- auth, DNS, file sharing, email server, application servers, web servers for internal apps, database server for internal apps. Usually sourced from a local MSP - or at least you had a support contract with them.
You didn't need a rack. You also had something that wasn't designed for a rack, so it could be in a secure back room with the switches, a UPS, a router, maybe some external storage... where it'd just sit quietly. Just has some big slow fans because that's all it needs.
Trust me, still a thing in small businesses, small retail stores, restaurants, etc.
