There is a business in my hometown that provides drop in child care. I'm not sure if it is a chain or just a local enterprise.My children are older so it wasn't in business when I might have used it (and I had fulltime daycare for them anyway) but you can use it by the hour. I believe the procedure is to go and fill out paperwork and have a "trial" visit with mom present so everyone can see what the facility is like, meet the teachers, etc. I think they usually have two teachers there at a time, and adjust for the crowd level. I'm not sure what their policies are or whose standards they have to follow (state daycare regulations or local occupancy numbers.)
I think it is probably true that larger chain daycare centers don't have provisions for drop in care but to say none do is inaccurate. As mentioned before, I believe KinderCare and Childnren's World both have had drop in options in the past. That would have been a last resort for me, but if it had been my only choice I would have used it.
Really, we can argue 'til the cows come home about whether the legal system SHOULD require mothers of young children to serve as jurors. But I believe we have established our feelings on that subject. No one has said, "Oh, I love jury duty and making arrangments for my small children is a breeze!"
But feeling that way and being allowed to skip it are two different things, at least in some jurisdictions. And after you've vented and raged about it, you still have to face the fact that if you are called, you have to be there and your children have to be somewhere else. So why not look at what your realistic options are and have some control over the situation?