I don't understand why you would say "But someone would be being pretty neglected if they did not get the help that PIP says everyone needs." when clearly you know that PIP doesn't get people the help that they need. They need their families to step in, be that to actually help, or pay for it, or both.
Also if you really can not do the most basic things, and have under a certain level of savings, and income, local authorities also give help.
That entirely depends on where you live.
Here the couple I mentioned earlier had to fight for help as the terminally ill man was classed as 'living with someone who can assist' even though his wife was disabled and he was her carer.
The 'help' they received from the LA was a wheelchair ramp that took 13 months to fit and finish.
He also had to use a bath bench for 12 weeks, then a motorised bath seat for 12 weeks before he could be assessed for a wet room (they rent from a housing association so HAD to have the assessment before a wet room could be fitted even if they paid themselves) - despite the fact even the LA's assessment said he couldn't use the bath bench, and that that bath seat would make the bath too small for his 6' length.
The same LA took 14 weeks for a blue badge, and 29 weeks for parking space.
The same LA then took 16 weeks to put a 'care package' into place to help the couple and that consisted of 2 visits of 9 minutes per day. This was removed after they had visitors for 2 visits then missed 2 visits (they were at hospital appointments).
It really, really depends where you live