If they are legal for batters, then can a pitcher wear a glove on his pitching hand? If the reason for allowing batting gloves is to 'increase the quality of the grip on the bat' then it makes sense for a pitching glove to 'increase the quality of grip on the ball'. I'm sure a batter would agree, because very few batters look forward to an errant cold weather or drizzeld rain, 100 mph baseball heading straight for his . . . . assorted body parts.
First the legalities:
Rule 6.02 (c)(7) Comment: The pitcher may not attach anything to either hand, any finger out either wrist
Second, pitchers may not want to do it. In Football the quarterback is allowed to wear a glove on their throwing hand and the only player that does that is Teddy Bridgewater.
Third, don’t worry about safety of the batters because most pitchers are using foreign substances anyways. (See what Trevor Bauer has to say about it https://www.sportingnews.com/us/mlb/news/trevor-bauer-mlb-pitchers-steroids-pine-tar/2qhjxr7i4yrq1t15yl99ysvp2)