Because most other teams aren't in the same luxury tax hell we are. Many will be under the cap this summer and several will even be under the salary floor. Some also view Crabbe as a potential starter, and he could start for some of the worst teams in the league like BRK or PHI. So, overpaying him is must less consequential to them.
In POR's case, it's not just about the money, although that starts to add up really quickly (do you really want a player like Allen Crabbe costing you over $100 million a year?), it's about the other penalties associated with being over the "apron" - the point $4 million above the tax threshold. Right now, we're projected to be $20 million over the tax threshold, it we do nothing, for the 2017-18 season. Declining Ezeli's team option get's us to about $14 million over the tax threshold, or $10 million over the apron, and that's without adding anyone to take Ezeli's roster spot. Being over the apron means you lose your bi-annual exception. It also means the amount of your MLE goes down. There are also much tighter restrictions on trades you can make. Basically, it makes it much harder to make roster moves to improve your team.
And, then there is the higher tax rate for repeat offenders. If we keep Crabbe as long as you suggest, we will be in repeater tax territory even if we don't resign Nurkic or Vonleh. A team that is a repeat offender that is $20 million over the tax threshold pays $4.75 for every dollar they are over the threshold. If we keep Crabbe, his salary in 2018-19 will be $19,332,500. At the repeater tax level we would be at, not even counting any raises Norkic and Vonleh get, Crabbe's contract would cost the team $111,161,185 per year. I can see Paul Allen shelling out that kind of dough to keep Damian Lillard, or maybe C.J. McCollum, or possibly Jusuf Nurkic, but $100 million a year for Allen Crabbe, no way.
We need to cut a shit ton of salary and we need to do it before next February's trade deadline and Crabbe has the biggest contract other than Dame of C.J. He needs to go, and if we want to resign Nurkic and Vonleh, Turner and Leonard will likely need to go before the 2019 trade deadline as well. We already have two max players in Dame and C.J. Nurkic will likely be a third, or at least close to it. You just can't have a bench player making nearly $20 million a year when you have three other max. contract players on your roster.
BNM