Overall I agree with you but I still think there are pros and cons.
In the case of Kucherov, first, given that his bridge deal was 4.77M, there is no way he would have settled for 6x8, but probably 7x8 would have been settled.
Using those numbers:
With bridge deal
- Locked up for 11 years before reaching UFA
- Locked up until he's 34
- Save about 2.3M the first 3 years
- Overpay by 2.5M the next 5 years
Without bridge deal
- Locked up for 8 years before reaching UFA
- Locked up until he's 30
- Overpay by about 2.3M the first 3 years
- Save 2.5M the next 5 years
The 5 prime years of saving here is key, versus locking up your star longer while he's in his prime.
Without the bridge you face a big dilemma when the contract expire. The player is still in his prime but just about to enter his declining years. Smart money is on letting him go and let another team overpay and make that mistake, bu then you're also missing out on some good years from the player.
I think if you have a bunch of young players hitting their prime at the same time, of star players already eating a lot of your cap space, not doing the bridge deal is smarter. If your team is lacking in stars, or you have a hard time retaining or attracting star players, maybe the optics of locking up you guy for an additional 3 years is worth it to you.