Reasons: Ignorant, Wise, and General
Ignorant:
People experience short ball times and get frustrated, not knowing that you can improve your ball times fairly easily by researching a few basic techniques.
People have only ever seen really old and relatively simple EMs. If they saw a modern pinball machine it would pique their interest.
People don't realize that scoring strategies are complex just from looking at a machine.
Wise:
People don't want to learn 100+ different rulesets and don't want the diminished experience of playing pinball without that knowledge.
Expensive, needs maintenance, takes up space, etcetera
Less strategically interesting than most esports. Pinball has little to no interactivity between players, compared to video games. People like multiplayer interactivity.
General:
Lots of people don't like games, period.
Lots of people don't like games that require reaction time or where mistakes are harshly punished.
None of their friends are into pinball.