Am I being petty and unreasonable?

I have a friend... she lives next door to me, and while we aren't great friends we do spend time together now and then and get along just fine. We used to hang out a couple times a week, but then she started working again last year around April. While she was working, they would ask me to go let their dog in during the day if the husband was out of town for work, before the day got to hot. I did that for them, I'm going to guess 3 times, for a week or so each time, the last of which took place while this horrible crap was happening to me. One day during all that I went to go let the dog in a little late (can you blame me for forgetting?) to find my friend hanging out on the couch. Seems she decided not to work that day and didn't bother letting me know.

After all this, I told another friend of mine that I was having trouble with the whole 'help me out' things, and this is where I'm afraid I'm being petty, because after having me do these favors for them 3 times, all I ever got was a thank you. If I ask someone to watch my cats or something, I'll bring them back a little souvenoir for their kid or a giftcard for them. All I was hoping for was some kind of gesture to say hey, we realize you're doing us a favor, here's a little something to say thanks. I would have been thrilled with a $5 St@rbucks card or a t-shirt for my daughter from wherever the husband was traveling to. I've also always thought it odd that it's the husband who always asks me to help and comes and thanks me.

A few months ago they went on a cruise. They boarded the dog, but wanted me to go over and water their hanging plants, I can't remember if it was every day or every other day, while they were gone. Of course I did it.
Up to this point, whenever they needed me to help them out, the husband, not my friend, would come and ask me to do it, then bring me the key before they left. When they got back, he would come pick up the key and thank me.

My friend stopped working around the time of that cruise. We hung out a couple times, but not much. See, every time I ask her to go do something she says she has no spending money. Not that any is needed to go walk around Target, but whatever. Some people are hurting for money, I understand that. The thing is, these people aren't hurting for money. She likes to brag about how much they have saved and in investments and how everything is all paid for so they have no car payments and stuff. She brags about the inheritance her husband will be getting when his grandparents pass away and the settlement she got for her car accident. They go out a lot together and she often goes to craft stores and buys yarn and fabrics and stuff. So I've never understood why she never has $5 to go out to lunch with me - we're talking McDonalds here, not some fancy Italian place or something. We can't afford that and my daughter won't eat anything other than chicken nuggets. But whatever, I'm not so petty as that I would refuse to do them favors because of this, but it bothers me. Just had to throw in that little bit of background.

Anyways, a few weeks ago they went on another cruise (see how hard up for money they are?) and the husband asked me to water all their plants in the front yard every other day while they were gone. I was hesitant about it because it is getting very hot around here and being in my first trimester I barely had the energy to water my own plants. But I said I'd do it. This time they didn't leave me a key because I was watering everything in the front so I just used the hose. However, I still expected someone to come by and let me know they were back and thank me for helping them out. Nope, I never heard from them. I saw that they had gotten home, and my hubby has seen the husband outside a couple times, but neither of them has stopped by or called me to say thanks. They've been home for about a week and a half now and I haven't spoken to either of them. My 'friend' emailed me some junk mail yesterday, but no personal message or anything.

So here is my question for all of you. Am I being completely petty in expecting them to bring my daughter a souvenoir t-shirt or something to say thanks? Especially after I've helped them out, oh, 5 or 6 times now? And am I being unreasonable to expect this friend of mine to have the money to go have lunch with me once or twice a month? And to at least come by and show me the pictures from her trip and say thanks? Or at least just call and say hey we had a great time, how about coming over for coffee? I'm beginning to wonder if I'm only a 'friend' because they need someone to take care of the dog or water the plants while their out having fun!

Please leave me comments on this - it has really been driving me crazy lately! Oh, and if you happen to think I'm not being petty and/or unreasonable, how should I handle it the next time they ask me to 'help them out'?