I am pretty new to Mathematica (and programming in general). Often, I use Mathematica to check some results (mainly consisting of linear equations) and I wonder why the equations do not equal 0. Then, (sometimes after 10 minutes or so) I find out that I forgot the Simply command (again). I then put my expression into "Simplify[...]" and get 0. However, I wonder, what is the purpose of this command? Why doesn't Mathematica automatically simplify "simple" expressions? E. g. I have the following expression:
-3 a66 + 2 (-a66 + 2 (2 a66 - a77)) + 2 (2 a66 - a77) + a77 - 2 (-2 a66 + 2 (-a66 + 2 (2 a66 - a77)) + a77)
which, only when using Simplify, reduces to
-a66 + a77
I don't see why any user would prefer the former form. So the only reason I could think of is that simplifying needs a lot of computational power. While this may be the case for "difficult" expressions involving trigonometrical expressions, I can't see why this could be the case here.
My Internet search doesn't give any results on this question and it's hard to imagine no one had this question before.
Note that this is not a rant but I genuinely wonder what the reasoning behind this is.