It annoys me so much I have to leave my desk and make a cup of tea to calm down everytime someone emails me a spreadsheet where they've done this!
There is no justification for this. Either:
A - you have set the important information to print and everything else is backing information. In which case you need two tabs, one with the summary, the other with the backing so anyone who wants to can trace it through but the important information is summarised on the front sheet. Or;
B - it's all equally important but YOU only needed to print part of it. In which case either select cells and use print selected or use clear print area before you save it in a shared location or forward it on. If it is the case that the bit you needed to print is the same bit everyone else will need then I refer you to point A above.
All that happens is that you send it on, the recipient prints it to read, or worse still when they've added their own work to it and printed it, the bit they wanted didn't print because it's not in the print area you dictated, they throw it in the bin, swear at you behind your back and have to go back to their desk, clear print area, and print it again.
I know I'm not being unreasonable when I say the only reason to do this is because you hate everyone you work with!
(Oh god that feels better)