Either lazyness or apathy. It’s just a fact. Almost anyone who is at church can take $10 and head to goodwill and buy themselves a decent pair of Mass shoes. I dress to the 9s during the winter every Sunday (hat, bowtie, sport jacket, dress shoes, belt, black socks, etc…) and it probably cost me less than $50 to get all of it. Around here, a decent button up shirt is usually $6.99 at goodwill, and a pair of pants are similar.
IN MOST CASES, if someone wants to dress up for Mass in America, they can make it happen. If they don’t, it’s their own fault. It’s all about priorities.
Like with voter id, they may have to go out of their way. They may have to [gasp] spend an hour or two getting it done. But it’s not that big of a deal to get one or two sets of dress clothes.