Pasta is cheap cheap cheap. I grew up poor with seven siblings and spaghetti with ketchup or margarine was a normal meal for us. In college, my roommates and I ate spaghetti with some regularity. We were all quite thin. I've never been crazy about pasta and pretty much stopped eating it once I was out on my own and had enough money for different food. I managed to get fat off other kinds of bread and sugar.
I do still serve pasta to my kids. Since I began low carbing, I've been making meals that I'll serve to them with pasta, like say chicken broccoli alfredo, and I'll eat it myself without the pasta. I know pasta is bad for me. It makes me hungry and sleepy. My kids? It fills them up and it does so cheaply. They're all in sports and quite frankly, to feed teenage boys without bread and pasta would be a real shock to our budget. Two of my boys can come in from practice (track or crew) and eat 2 peanut butter sandwiches *before* dinner. I can't even imagine what my grocery budget would look like if those boys followed my LCHF eating plan.
My boys eat lots of stuff I will never eat again in my life, e.g. cereal, pasta, rice, fruit punch, sugary yogurts, etc. I know that stuff's all processed junk that leaves me feeling hungry and awful - I don't miss any of it. What I don't know is how much damage I'm doing to them, if any. I do try to keep things into perspective for them and let them know they can only eat this stuff with regularity because they're young and active but once their metabolisms slow down they'll need to approach these foods the same way mom approaches bagels and chocolate chip cookies. Still, our kids eat much healthier than my husband and I ever ate growing up so I think they should have a better handle on nutrition going into their adult years. At least I hope.
ETA: My daughter, on the other hand, does eat pretty low carb, and rarely eats bread. At 20, she's the oldest of our kids. She's a trained dancer and rail thin. She primarily eats chicken and vegetables, although she still enjoys plenty of sugary treats.