Because you're not getting Byram for Cirelli especially given salaries. Cirelli is the top player on my wishlist for the Sabres make no mistake, but someone giving you equal value for him and providing you with the cap space is adequate. No one is gonna overpay you for him. If you guys are hellbent on his value then keep doing cap gymnastics, lose depth, lose Stamkos etc. There's gotta be a 1% chance our GM aquires Byram then turns around and gives him away for a Mitts equivalent who makes more than Byram/Mitts not even 30 games after getting him.
I'm not shitting on Cirelli or anything quite the opposite but his contract and your cap situation and need to resign your franchise captain and icon and/OR add depth to continue with your current core is a real thing. I think people offering top a top 12 (at worst) unprotected pick + all the while providing cap breathing room are closer to reality than thinking Adams turns around and flips Byram is.....personally and respectfully.
Tampa doesn't have e to move him, period. They absolutely shouldn't be moving him unless they get what they want in return. There are other dmen Tampa should focus in anyway, either through trade or ufa. No need to move Cirelli to Buffalo.
Tampa is also more than able to clear enough cap with lesser moves to improve the roster. Whether Brisebois is willing to take the big hit on trading Jeannot for peanuts, after what he paid for him, is another story. Sheary should also be moved, and if Tampa is going to add an RD, they should trade Perbix as well. They can have approximately 17.5 in cap space after these potential moves. They can still re-sign Stamkos and a ufa dman in the range of DeMelo, while.filling in several spots(mostly 2 or 3 F spots in the bottom 6/extra F), with a combination of Syracuse promotions and cheaper ufa's like Motte. The final F spot would take a hit, as the room wouldn't be there for some of the options, but dependent on exact contract values for other players, they could still spend around 3 on a middle 6 F that could play up. Until Stamkos re-signs and Tampa either signs or trades for an RD(if they do), it's hard to say exactly how much they'll have to work with.
There's no reason to trade Cirelli and create another hole in the top 6 unless Brisebois guarantees that by doing so Tampa addresses a position of need(a top 4,.more defensively sound RD) that either has term or is going to sign right after. I'm sure the 1st rd pick could work towards one, but it's no guarantee. I'm not in favor of moving Cirelli anyway, but especially not to a.division opponent and not for what Tampa needs(without more hypothetical trades to address their situation).