Why is NOLOCK implemented like that?
SQL Server by default operates under Read Committed isolation. 

If you want SQL Server to behave more like other implementations, what you're looking for is either Read Committed Snapshot Isolation, or Snapshot Isolation.

You can read more about them here. 

Full disclosure, I am a Brent Ozar Unlimited employee

Using NOLOCK or Read Uncommitted is generally frowned upon for serious production use, as it can allow dirty reads and other unintended artifacts while modification queries are in progress.