For the same reason as any accessibility mechanic that’s not catered to allowing people with a disability to play the game.
It removes barriers for those which do have those example 10 hours.
What audience does a specific game cater towards? That’s how it’s got to be designed.
So, who does LE cater towards? With the words of EHG on the Steam page ‘veterans and newcomers alike’… which translated means ‘we cater to nobody’ in reality sadly. Sounds nice, works like crap. Only a distinct few games ever managed to do that and only those only did partially so.
Well then… how are the design-decisions in the game handled? Mid-tier loot Hack’N’Slash players. Not utter beginners (D3, Chronicon) and not in-depth players (PoE 1, PoE2) either. It’s positioned roughly like Torchlight Infinite. Not as complex, not as simple.
So then following that what does the expected play-time of that target audience look like?
Longer then D3, less then PoE as well. Middle ground is to be expected for the core target audience based on design. What EHG wants to cater to and what they did cater to since years are two different things, not managing to cater to those they actually wanna cater to is their failing. Changing it though is a death-sentence for every game after being established, alienates all existing customers and barely ever goes well.
So then what’s the distinct play-time expectation in numbers? D3 it was 50-60 hours for a invested player. PoE it’s 200+ hours. Mind you, per league, hence all 3-4 months. So LE being the middle ground we can expect anything from 100-150 hours.
So this leaves us with the ultimate question related to the ‘Why not?’: Does the game actually provide respective amount of replay value to uphold this with a cycle of ‘1 played, 1 off’ league/season/cycle?
The answer is: No, it does not.
Which is a design shortcoming from EHG for the moment.
Mastery respec reduces this replay-timeframe substantially. It’s a viable implementation when the expected play-time comes close to the 150 hours, it’s a detrimental implementation when the play-time is below 100 hours.
The current play-time of LE is at best 50 hours, the content simply doesn’t allow much more unless you go into the extreme min-max areas which always are highly repetitive (and leads to 500+ hours playtime comparatively for PoE 1 as example). They are to be excempt from the positioning. Tourist players simply ‘looking in and leaving after’ are also to be excempt, they are not core target group.
So that means the play-time is potentially lowered since respec allows reduction of that and hence reducing long-term the returning playerbase as ‘they’ve seen everything already’. If Cycle 3 provides updates which aren’t utterly massive in content then we’ll see a drop overall in returning players. Cycle 4 will not rise unless the content becomes vastly bigger either… and so on. This will uphold until the design-position on the market and content-breadth are aligning with each other.
And mind you, the current issue is that already LE has below expected quantity of content… or better said perceived content. That’s to large degree design errors from EHG, which are understandable… but they need to work on that, until then people won’t stop saying ‘This game has not enough content!’ because they simply messed up giving it to the players in a viable long-term grinding-able basis which feels rewarding for the ‘mid-tier’ Hack’N’Slash player for years to come with the pace of development the studio can handle.