Kids would instead be locked into shit schools because their parents aren't there, don't care, or simply don't have the time to research alternate schools, but (yay!) private and charter schools get to siphon off money from the public school system.

Vouchers that immediately squander the social mobility provided by public schools by placing them in an opportunity to go into a financial death spiral the moment those who can afford to leave and take the tax money with them while those who don't have the opportunity jump ship to a public school are left high and dry in a local education system bleeding viability. Public schools exist as an egalitarian institution, why deliberately fracture them into pieces for any reason other than to kill the whole idea off? Tangentally the idea is often pushed underhandedly by some evangelical types to shovel taxpayer money into religious schools in a way that isn't currently legal to do outright, but that's a problem adjacent to the idea rather than the main problem with it.

My anecdotal experience is that none of the ~10 or so pro-Charter School people I know are in the bottom 30% of incomes (even talking about bottom 30% of my network). Most of them reference the curriculum and their objections, whether from religious beliefs, pseudoscience, or similar. Others planned to send their kids to private school anyways and want to save money.