I'm left-handed and grew up writing English. Except in the cases that I take special care to hold my hand somewhat awkwardly off the page, virtually everything I've ever written has some amount of smudging. I have vivid memories of my graphite-coated hand in primary school. In addition, it's harder to see the flow of the word; your hand covers up everything but the last letter or two.

It's clearly something that impacts different people in different ways.

I can imagine a person writing a B using their right hand moving left to right. To me (maybe in hindsight and biased) it seems more natural to write B that way. But there may be cultures who write B but write right to left or both ways boustrophedonically "as the ox plows" like ancient Greeks did.

My reasoning is once the vertical line part is drawn it would be awkward to go backward for the two bumps. Especially if using ink not chilling it into stone. You would end up smearing the ink.

But even with stone or ink you'd have more room on the right for spacing between the previous and next letter.

We are used to things the way they are today and the way they are taught in school. Before the "standartization" of the alphabet, it did not matter whether letters were rotated or reflected; for example, originally the letter A was written upside down (with the bull's horns pointing upwards). Even the ordering of letters in the alphabet was not seen as essential; it was introduced first as a handicap for easy learning, and then, in some languages such as Greek letters started being used as numbers.