Because entry-level mountain bikes sold at bike shops commonly are used for multiple purposes, including commuting and casual leisure riding, they pretty commonly have fork lockouts on otherwise not especially great forks. On higher end mountain bikes, true fork lockouts are actually a little less common because a true, hard lockout is not frequently helpful for real mountain biking, outside of cross country racing where the ability to sprint out of the saddle is important.

If you never want suspension, I strongly recommend just buying a bike without any suspension as it will be far lighter, stronger, and more reliable.