People that work and do not have children are just in another place in their lives right now. They are not being rude, they just do not have any idea what your life is like.. They are working hard on their careers and enjoying doing things for themselves. (My husband and I were like this before our child). If you want to be included make an announcement.. "I would love a night out, when is the next time you all are going for a happy hour."..
Is your child in daycare? When I was working full time, our daughter was in daycare and sometimes we parents would get together at a park and let our kids play on a Sunday afternoon or Saturday morning. . We would all take our own lunches and after a set time, we would go home so the kids could get their naps or go home and start the bedtime routine.. .
Or after school we would meet at a place with a playscape and let the kids play while we had a margarita..
Also in our neighborhood, we had lots of neighbors with young children and we would meet in one yard and each take our own beverages and just let the kids play.. Sometimes, the children would beg US to go go inside.. Hee, hee.. Good times..
Try sending out a invitation to the families you notice with children to come over for a "meet and greet." Try to do this on a Sunday afternoon like at 4:00.. Serve watermelon, chips and dips.. If you drink you could have beer and wine available, but also tea and lemonade.. Maybe a little splash pool for the kids..
It is just different, but can still be fun when you find those other parents out there.. We always thought we were so different than everyone else and then one night we looked around and laughed with 12 parents and 8 little kids running around, we all looked different, had all types of different jobs but realized we all had the same joys and worries.. "how would our kids turn out and were we being good parents".
Hang in there.. You may have to step out of your comfort zone to start meeting others.. It will be worth it..