I highly doubt we need a guide on how to convert Bitcoin to fiat, a simple search would reveal may options of doing this.
Why most persons uses centralized exchanges such as binance is they are more renowned and widely advertised than most decentralized exchanges and even newbies or old members are excluded of the usage.
Like in my part of the world many newly introduced crypto enthusiasts can't equally differentiate between a centralized and a decentralized exchanges in terms of the advantages as it concerns privacy and security. To them they are using an exchange platform and the transactions are cool, and that's all that matters but with no clue on the advantages and disadvantages that comes with each.