The primary reason you don't find social media sharing buttons on Wikipedia is they violate the Wikimedia Foundation Privacy Policy by loading you up with third

The primary reason you don't find social media sharing buttons on Wikipedia is they violate the Wikimedia Foundation Privacy Policy by loading you up with third-party tracking cookies. The second reason is they are ugly as sin and most of the community hate them. A distant third reason is you then have an argument about neutrality and inclusion - which sites do we include and why. Which is an argument nobody seems keen on having given reasons (1) and (2).