Quoting Bree & Sade's Mommy:" My sister always had her kids front facing really early on, and our kids are really close in age so ... [snip!] ... the time, but if one isn't available, she won't make him. Really upsets me. But if I call her out on it, she just gets pissed."
My 5 year old is in a booster, and will be for years.
There was one time recently where she didn't ride in a booster and I felt like complete smurf for it (and drove like a paranoid granny).
The only reason was because I was babysitting a 2 y/o, and his carseat, my 1 y/o's carseat, and the booster do not fit in the back.
Normally I just wouldn't go anywhere but my mom had knee surgery and her cast broke apart the night before. Her ride to the doctors flaked out on her and my da couldn't leave work to take her (and spending another day without a cast wasn't an option, it was her 3rd surgery on that knee in the past year because they kept putting her in a brace instead of a cast so whatever they were fixing kept re-tearing).
Scariest 15 minute drive of my life, and will never do it again.