In these day, without the easy availability of the teaching Church, fplk tend to be unsure, so they tend to make up their own rules, which are stricter than the Church - in other words - scrupulous.
Saw a post here about what a priest said about basketball and not condemning going to a restaurant on Sundays. I think trads are so used to being the polar opposite of secular society....drawing that line in the sand....opposing anything outside the trad bubble, that when they hear something is ok, they don't know what to do without a strict condemnation. There is more to the faith than hell fire and brimstone. It was the cornerstone of modern civilization. In reading this thread, I agree with what you said. People are taking it to absurd levels to try to avoid a venial sin. Only plugging in a crock pot to cook...avoiding recreational sewing.. fear of eating at a restaurant.
Modern issues with the Church aside, life and society have changed a lot in the last century. 100 years ago, shops were not open on Sunday, you wouldn't be able to (or have the need to) travel hours to get to Mass, and if you were male, you were drafted into WWI. 100 years before that Baltimore became the first city to have gas powered lights, Mississippi became the 20th state. 100 years prior to that, there were about 65,000 Catholics in the US (1.4% of the population in the thirteen colonies). Many of the colonies were very anti Catholic and abusive to the faithful. My point is that we are a blip in the radar of the Catholic faith, yet the world changes quickly around us. Just try to do what is right. If you are worried that the marathon is going to conflict wit your Sunday obligation....Ask your priest...He should be a stronger moral authority than the anonymous folks on CI.