Do conference attendees care about conference bags?
Having gone to quite a number of scientific conferences, my observation is that the degree to which attendees care about conference swag (both bags and otherwise) is inversely correlated to the number of conferences that they have attended.

Bags and other conference swag is wonderful, magical, and exciting when you haven't gone to many conferences.  It's a visible sign of scientific merit that you can even plop onto  the counter at the grocery store!  Forget bags, I've known people who have even saved their name badges as keepsakes.  For graduate students or occasional attendees, for those who go to only one or two conferences per year, these things can be very personally significant markers of acceptance and belonging.

As the saying goes, however, familiarity breeds contempt.  At this point in my career, I have a cupboard full of canvas bags.  When I go to a conference, I mostly just ignore the swag, and most of my close colleagues do as well.  But their graduate students, bright-eyed and so excited to be giving their first poster presentation ever, are likely to feel quite differently.

So, would people be OK receiving nothing but their badges? In many cases, it's just fine to give people nothing but their badges, and for more specialized meetings, that's just what they do.  But if people are paying a hefty fee to be there and there's a lot of graduate students or occasional attendees, why not give the little bit of extra to let the people who want to feel special are able to feel special?  A decent custom tote bag can cost as little as $1, so it's a remarkably small cost for the conference (far less than the leaden afternoon brownies mandated by the contract with the conference venue).  It will make some of the attendees very happy, and the people who really don't care can simply shove it in the back of their bag closet like I do.