I see the benefit of tamper proof receptacles, my mother said I used to play in the outlets as a kid and I was lucky I didn't get fried. Tamper proof outlets are to supplement but do not replace parental supervision.
My son is almost 9. We has regular old school receptacles and never used the bs plastic baby proofing plug things. We had a baby gate setup at the top of the stairs and I baby proofed one cupboard as his mom thought it wS funny to let him open the Tupperware cupboard and pull everything out, so I had to put a stop to that.
My work around for this "lack" of baby proofing? Keeping an eye on him at all times.