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InnoDB (MySQL's default storage engine) implements MVCC using undo logging and background purge threads. It scales to highly concurrent OLTP workloads quite well. It doesn't work well with OLAP workloads / long-running transactions though. The oldest active transaction will block purging of anything newer than that transaction's snapshot.

Yes, MySQL has read locks.

But I don't believe SQL Server does.

SQL Server has had MVCC since 2005.

Yes, but doesn't it require opt-in to enable snapshopt isolation? Most T-SQL devs will probably default to locking (TABLLOCK, etc) becuase that's what the bulk of google search results for "how do I fix my broken query?" tell people to do: it's only very, very rarely do I see a stackoverflow or dba.se answer that mentions MVCC-related topics.