Some people enjoy doing that work, but most people did not, and I was often the last resort because a random club or activity could not find suitable help in time. So had to step up when a friend or acquaintance asked.
I think there is some misguided view where in "the good old days" people designed everything by hand. From the perspective of someone who had to make 10-20 of those a year as a volunteer, I can say it came at personal cost, often caused distractions from the actual event, and there was not enough people who stepped up to get it done. If it was so enjoyable we would have no problems finding people doing the work and that was not the case.
The posters and designs were often rushed out late night by the closest person you can find who had a copy of photoshop on their computer. If we had AI back then, I would bet you 100% it would be the preferable solution and no one would bat an eye. It wasn't the type of work a lot of people wanted to do, could do properly and is willing to do for free, at their spare time, rushed for a deadline.