Is there a club anywhere that is based on the most obstreperous member serially making new demands every few months and the rest of the club rushing around to ask what he/she really wants, frantically adjusting everything to the new norm and then patiently welcoming the same procedure the next time, again and again ? What if they refused to and left said member to simply like it or lump it - if he walked off, then what ? Would the member be anything but delusional in assuming they would weep at his leaving, that the entire club would cease to exist without him ? Also, how easy would it be to demand from him any penalty in outstanding membership subscriptions, bar bill, etc. ?
Why should the EU do anything but tell the UK what the EU's terms are and wait to see what the UK does, at best be ready to listen to the UK's latest demands but otherwise promise nothing outside the EU's framework ? Is there the slightest realistic justification for the presumption that the EU is trembling at the thought of the fabled golden UK goose's egg no longer being laid ? Has the EU made any statements regarding forcing collection of any "exit charge" - is there any realistic prospect of the EU forcibly collecting this in the event that the UK "walks away" without a separation agreement ? Would the debt not simply remain a debt and be raised if ever the UK came to ask for anything again ?
Of course the UK can "walk away", in which event the EU is at liberty simply to proceed as they will including as if the UK was a complete stranger with no previous history (come to think of it, maybe the most flattering way to see the UK).
At some point any relentlessly self-indulgent brat will exhaust all patience and lose friends and be left to fend for him/herself. The brat will quite possibly be very slow in realising that the past casts a long shadow, mistrust has a very long half-life, long dead daddy's deeds and reputation no longer smooth the way, hoped for allies and friends disappear into the long grass, but reality will inexorably force its way into his/her psyche. Those with the relevant curiosity will look on with some interest, possibly (but not at all necessarily) with sympathy, how low the formerly great have become.