"Need" may be too strong of a word but I do enjoy having the option. I never carry my shield with the safety on, but as Bozz10mm said, it's nice to have for safe re-holstering or certain other situations.
Also, I can pocket carry my bodyguard 380 without a holster (safety on) if I choose. It lets me have less bulk in my pocket, which is important with some of my pants due to pocket size, but still have the gun in a safe state for carry.

As we have been known to say on this forum -"It's better to have a gun and not need it than to need one and not have it". Same applies to safeties IMO.

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Stay protected my friends.