To be fair, the OP did say “some brands” not ALL bikes. Also, I have one of those Walmart bikes and I pity the foo who owns one. On my very first ride, my pants tore the chain guard off. Pretty sure it was there to protect my pants. Then when I came to a stop, the seat exploded. Springs, nuts, bolts and washers went flying. I had to gather them up again and try to piece it back together to keep the seat usable. It’s ridiculously heavy too. If you can’t afford a nice new bike, I recommend buying a decent used one at a garage sale or something. I don’t agree that they will serve the vast majority of people just fine.