I started quilting on my own back in the 70s before there were rotary cutters and such. As a senior in high school, I was intimidated by the "little old quilting ladies" that I have since become. Back then the books/designs didn't give you many directions. Just pictures of a block or historical quilts with pictures in black and white...
Anyway, I didn't know about pressing seams to the side for many years and happily pressed them open. They've been just fine open. I have a whole list of reasons, but basically I feel that with machine sewing pressing seams to the side is just a leftover artifact from hand sewing. Not to mention that we have irons now that plug in and don't have to heat on the wood stove.
Although periodically I try and do what the quilt police say, I hate pressing to the side. A lot comes from what you are used to, I am more accurate pressing open. I never have to worry about what side to press to or how the blocks come together. I really really hate how it looks when you press white on white seams to the side, big heavy line that shows up. I machine quilt and feel the open seams quilt easier, less bunches of stuff. And really -- who has time or desire to clip out stitches so the seams can nest around each other. Well, obviously, a lot of you do, but not me!