Can someone please explain to me why the yearly cap hit and actual salary paid are not the same?
Lets look at these two contracts. Both 7 yr 42 million dollar deals, both structured very differently. I'm going to ignore the signing bonuses as that's a different subject and just looked at the yearly compensation:
Lucic: 8m, 8m, 7m, 6m, 4m, 5m, 4m
RNH: 6m, 6m, 6m, 6m, 6m, 6m, 6m
So there's several reasons why it's advantageous to both the team (if they can afford it) and the player to receive more money up front and have it tail off towards the end of the contract.
1) Interest/investments - Lucic would have in the first 3 years earned an additional 5m that he's now getting interest on that will compound long term. If he's getting a 10% return, that's an extra $500,000* that RNH will never ever see - despite the fact that both have 7 yr 42m dollar contracts (assuming both invest the same way, yada yada yada). *Obviously not exactly - it's probably more, as the interest is done yearly, and would be compounded upon - but you get the idea.
2) Less risk to the team. Regardless of one's individual thoughts on these two players, some people look at RNH and his contract and think yuck - 4 years left at 6m AAV, and he's owed 24m over that span and he's not playing at a level worth that AAV. As long as the player performs, there's no issues, but if his play slips at all, moving a big contract gets harder to do with the more salary owed on it. Lucic for example in his final 4 seasons will only be owed 19m. So while contending/cap teams look at the AAV, every team has a budget, and ML having 5m less being owed to him (if both players are just as effective, yada yada yada) will make him easier to move down the road should they need to do it. Obviously there's a little more to it then just that (age, position, effectiveness, etc), but you can see how it could be a factor depending on where you're trying to trade him to.
3) Cheaper to buy out and more guaranteed money to the player if they are bought out. Again, looking at these contracts, if Edmonton for some asinine reason decided to buy out both contracts after 3 years (we'll pretend that RNH gets bought out at 66%), RNH would cost EDM 15.84m to buy out, while Lucic (ignoring signing bonuses and pretending it's straight salary) would cost 12.54m. Would still suck, but that's still money saved to make a problem go away.
So there's lots of reasons that are in both parties best interest to be allowed to have fluctuating contracts (aka back diving contracts) that have absolutely nothing to do with circumvention. Basically... every player should be pushing for these types of deals (regardless of length) and every team should want to sign contracts like this as long as their budget allows for it - as there's very little downside and several - abet minor advantages.