Referring to real services that serve bitcoin and earns bitcoin like Mixers for example
In descending order of profit they make (my own speculation without any solid data):
Centralized exchanges like Coinbase, Gemeni, Bittrex, etc.
Mining hardware manufacturers like Bitmain
Payment processors like Coinbase and Bitpay
Gambling sites like Primedice
Semi-decentralized DEX where they run a server and get paid in trading fees like Bisq
Semi-decentralized CoinJoin services like the honeypot called Wasabi
Wallet developers like Electrum running a side-service (TrustedCoin) for their users