More accurately, GB doesn't care. Only NI and ROI care. And you either create the border and keep NI, or NI leaves the UK and joins ROI or simply becomes independent and joins the EU. But NI wants access to both sides equally, hence the prototcol is for NI, not for GB or ROI or the EU.
So when you say "we don't need that customs border at all", it's not about you at all. But without it, you lose the NI. And the NI loses access to GB.
The choices for the NI are:
Lose GB, keep EU.
Lose EU, keep GB.
No changes because of the protocol.
Right now, all parties involved are for the protocol, so that's how it's going to play out.