Yes but shouldn't that choice be up to the individual church, church members and their personal convictions?
The jeans at a wedding argument doesn't make sense to me, because not all churches abide by the same standards of modesty. At my church it is perfectly normal and acceptable to wear jeans, t-shirts (with or without writing on them), tank tops or even a strapless dress. Our church is "come as you are". So perhaps someone is used to that sort of church, and when visiting or deciding to attend another type of church, haven't caught on - especially if they are not the only ones wearing less modest clothing, and they've never been approached about their choice of clothing by church authority, then it's quite easy to believe it's socially acceptable.
Besides - I've seen many a beach wedding where everyone was wearing jeans
Now for instance, someone pointed out the example of seeing ushers wearing t-shirts or tank tops. Obviously, the pastor has no issue with it, otherwise he would not have them as ushers! Obviously it's not a church that adheres to strict modesty standards. So why should anyone else care?
I guess what I'm trying to say is - if you, personally, feel best and feel like you are giving God your best by dressing your best, by all means, do so! But there is nothing in the bible saying "thy t-shirt shall not bear logos in the presence of thy temple". Nor are there any verses saying a woman should cover as much skin as possible (verses about modesty actually only refer to braiding one's hair and wearing jewellry, which interestingly enough, many people who use the verse in Timothy to explain their modest attire often do both of those things).
So why does it bother you if someone doesn't carry the same convictions in a church where, due to the obvious fact that those who do not dress modestly are not being approched by the pastor/preist, tells me it's not a rule for the church but rather your personal opinion.
My personal view on things like this that are not direct commands from God (but rather, are mainly man-made rules and standards) is that if God wished these people to do things differently, would he not lay it on their hearts in conviction? And if he has not, why would one then think it is their job to tsk tsk about it? Do they think it's not possible for God to make up his own mind whether to lay conviction on any given person, but rather that they need to step in and do it on God's behalf?
If someone is having premarital sex in the pews on sunday morning, sure, absolutely step in and tsk away because God makes his opinion quite clear on that subject
But I've looked extensively in my own research and have never found anything in the bible about women covering their shoulders.