Because he's not that good lol. He's an average 2nd pairing dman. If he can bring back a top-6 F or 1st+, you take it and run. He is replaceable.
Weegar, Kylington, Zadorov down the left side and then Poirier for years to come. Trading Hanifin would barely hurt this team next year (Kylington can replace him directly) and we can bring back a 1st or top-6F. That's a huge win in terms of maximizing the value of our assets.
You'd be comfortable paying Hanifin 6.5? Even 6? That is way too rich for a #3 LD with limited offensive upside. I don't hate Hanifin but that money should be better spent elsewhere. Boston can't afford Grzelcyk at 3.6875 past this year and just signed Hampus Lindholm (who is miles better than Hanifin) to 6.5. Kings just signed Mikey Anderson (a similar 2nd pairing LD) to 8 years at 4.125. Golden Knights just signed Brayden McNabb for 3x2.85. Colorado signed Girard (coming off of a better season than Hanifin has ever had) 2 summers ago 7 yrs 5 mil. Morrissey (who is miles better) at 6.25. Cernak 5.2x8.
Even Pelech (who is a legit top-pairing D, significantly better than Hanifin) got 5.75 after playing on the top-pair leading his team to back to back ECF's.
Contract-wise, something between 5-5.5 is fair value, anything more than 5.5 is too much. And even at 5.25, he's still a replaceable asset. Kylington (and eventually Poirier) should step into that 2nd pair LD spot at a much cheaper price and provide similar value. Not saying we should let Hanifin walk for free, but if he's bringing back a 1st or similarly-aged top-6F that's a great move for our team.
That is an absurd overvaluation of Hanifin. Pulock is a 1D who anchored a D core to back to back ECF's, within one game of the Cup Finals. Playing over 22 mins a night, anchoring the PK and playing top-pairing night-in night-out. When Tanev went down in the playoffs last year our whole D crumbled and we added Weegar to shore up the left side. Hanifin is currently probably our 4th best dman, arguably 5th if Kylington were in town. Pulock as a comparable isn't even close. Better comparables are McNabb, Mikey Anderson, and (on the higher-end) Girard. I bet if you ask Isles fans if Hanifin and Pulock are comparable they'd laugh.