Home made ones taste sooo much better too!!
Yeah, we all prefer peanut butter in ours (preferably crunchy peanut butter), but other people like chocolate chips, red hots, and other taste-specific goodies.
Well, sure - if you can't easily find the premade sheets; and they
are expensive. But don't forget how much easier clean-up is with the purchased sheets

.
One bowl for mixing, which goes right into the dishwasher. One pan into which the Rice Krispies are dropped, which -- again -- goes into the dishwasher once the treats are gone.
In my book, that's not trouble -- not when you consider that homemade treats (made with store-brand cereal) are a cheap snack and the purchased ones are quite expensive.
The homemade ones are tastier, but if your kids go to a school or daycare where only storebought pre-packaged treats are allowed, or if there's a kid with allergies whose mom wants to look at a package before allowing her kid to eat a treat, these are really handy.
I can understand the taking-them-to-school thing. You have to abide by school rules; however, I'd be surprised if any moms used to dealing with allergies didn't already know what's in Rice Krispies, and if they're at my house I'll certainly tell them what's in the treats. I wouldn't buy an expensive product just on the off chance that someone has an allergy.
For those of you saying they are just as easier to make and taste better, I'm sorry but I disagree. They are always a sticky mess, hard to spread, stick to everything except the darn pan I'm spreading them in and they are NOT as sweet as the pre-made. Clearly the pre-made ones must have added sugar and probably vanilla too.
If you're ending up with a sticky mess, you're not using enough marshmellow. With enough marshmellow, the stuff clumps together and forms a ball -- it doesn't even stick to the bowl in which it's mixed, if you do it right. If you save the butter wrapper and use it to press your treats into the pan, you won't even get your hands dirty.
My overall evaluation of the topic: Many people today just never learned to cook. I grew up making everything from scratch, so it's very easy for me. When you've done it for years, you learn little shortcuts to personalize things as you like them and to avoid messes.