I'm frustrated by the all-or-nothing tone of many of the posts. A wedding does not have to be "all about the guests, accommodating every possible desire and need" on the one hand or "all about he bride and groom and what is meaningful to them" on the other.
Nor does something need to be intended as a snub or or a personal rejection or a passive-aggressive statement of "I'm inviting you because I have to/want a gift, but I don't really want you to come, so I'm going to make it really difficult" in order to be a "message." As several posters said, and as I believe the OP meant, a "message" doesn't only mean one deliberately intended to be sent by the hosts. It can also be, as they pointed out, simply the inevitable result of making a choice. The location and time were more important to them than the convenience, and likely attendance, of the guests. That isn't "wrong." There may be EXCELLENT, unselfish reasons for those preferences, as some posters have suggested, but the bottom line is still the same: time and place over guests.
And it doesn't mean it is wrong or rude, and I don't think anyone said it was. And it doesn't mean that people get offended, even if they are disappointed. (Nor did the OP say she was "offended," if memory serves.)
Conversely, the hosts are deluding themselves if they think that no one is going to see it that way. They don't get to decide how others are allowed to feel about their choices. It's just as wrong to have the viewpoint of "But it's Ourrrrr Daaaaay!!!" as it is to have the viewpoint of "You have to do it for the faaaaaamily!" You make your choices, the same as anyone must. And then you own them; you don't excoriate people whom they disappoint or hurt.
LadyL, I hear you. While it is true that a wedding isn't the same as a dinner party, which is SOLELY about the guests' entertainment and comfort, it's still true that the hospitality obligations of hosts don't entirely fly out the window just because it is a wedding. This kind of thing is an unfortunate byproduct of the trend for HCs to host their own weddings; it can be tricky to be both the guests of honor and the hosts. My daughter has always dreamed of a winter wedding, but summer it will be, because that is the most convenient time for her fiance's parents to get time off work (they must come from overseas). I am proud of her for making that considerate choice.
Now, of course it's true that it's virtually impossible to make plans that are the most convenient for everyone. (For example, the schoolteachers and students in our family are going to be un-thrilled at another Labor Day weekend wedding.) And we are talking about things like dates and venues, not something like agreeing to get married in an unacceptable religious tradition or having 500 people instead of 10 or waiting two extra years or something -- that is a different matter. But I do think it's smart as well as considerate to try the best you can to accommodate your nearest and dearest -- such as giving up your preferred season in favor of the groom's parents' work vacation time and moving the festivities off the mountaintop so that Grandma can attend.