When you’re developing code interactively how often do you set a variable and then display it to test the result? You can do that in one go using variable squeezing.
Normally you’d do:
PS> $test = 1
PS> $test
1
Set the variable and display the contents as two separate actions.
By enclosing the first statement in parentheses you accomplish both tasks
PS> ($test2 = 2)
2
Great for interactive work but you don’t want in in scripts as you’d be getting output every time you set a variable value!
Richard Siddaway's Blog 
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As for..
“Great for interactive work but you don’t want in in scripts as you’d be getting output every time you set a variable value!”
Except for when that is what you really want to happen, vs, spinning up progress bars, etc., though progress bars are the more elegant solution, though they don’t show you if a variable is changing inline as you may want to know.
So, yep, I can agree that the greater portion of the time, maybe avoid this, but all out avoidance, I not yet in that camp.
As with all things there are exceptions. The general rule of don’t do this is scripts stands. if you have specific circumstances where you need to do this then the rule is overridden. Only you know what your code needs to do – its the mark of an expert that you know when to override the rules