Why don't strong players do puzzles on chess.com?

A puzzle doesn't have to specify a particular number of moves.
A study is often something that's composed.
Its a misconception to think that tactics only pertain to tactics and not to positional play.
Or that positional play only pertains to positional play.
Or that a move can't be both positional and tactical.
Does all that seem Obvious??
The point is that players have these misconceptions or they are gradually indoctrinated in.

'Calculation' and 'Observation' are different.
Observation pertains to 'what's going on in the position'.
Calculation is the preparation and comparison of precise sequences of moves.
See the difference?
Failure to appreciate the difference will result in gross inefficiency.

Ok, clear. Thanks.

In my early days on the puzzles - I wanted to find ways to be more efficient.
And yes - I wanted to improve my Tactics rating whether mistakenly or not.
I devised methods to be more efficient but without 'skipping' anything.
For example - try looking at the two kings first and their situations.
Or - if you're stumped ... try that basic.
They're always both there. They're the most important pieces.
If progress isn't happening intuitively or just not happening ... then try method.
The queen situations are next. Vulnerability and offensive potential.
The queens for both side.
And then so on down to the pawns.
This helps to identify what's going on and account for all the material on the board.

It stops at 4000.

Master-level players have already reached the point of diminishing returns, when it comes to solving puzzles. They know how to calculate well enough. Doing additional puzzles isn't going to help them improve by much.

They get more out of playing and analyzing, at that point.

As to how different titled players such as masters and GM's prepare and condition and train themselves for high-level chess I imagine there are tremendous variations in their routines.
From player to player - from month to month and so on.
Regarding tactics - openings - endgames and various kinds of week to week preparation for tournament play ... I also imagine they don't all tell everybody exactly what they're doing.
Regarding 'no longer need' ... isn't it clear that top-level players know better than lesser players 'what to look for and to look at' in positions?
I think you'd find they choose their initial calculations better than lesser players.
Somewhere between observations and calculations ... forming candidate moves to compare. 

Wow! Before my comment, practically no one had posted anything.

That is generally how it works when you comment first