Interesting theory about production technical level. You might be on to something. Could you extend the paragraph or maybe provide a link explaining the basics?

@RobertHarvey In the answer to "What is the history of why bytes are eight bits?" (also linked in my question) there is the following sentence: "Binary computers motivate designers to making sizes powers of two." Did I misread this too? What do both sources mean in your opinion? Just saying "you got it wrong" is not really doing it for me.

Interesting point about UTF, although being slightly off-topic. Floating point byte (or bit) size is an endless battle between memory and precision where you just have to live with one or the other. Good point about bit arrays too.

Thank you. Your answer is spot on and you brought references. You have my vote. I realize though if what you say is true it is also impossible to prove. Can´t prove the non-existance of something. I guess I should really interogate the ones claiming "convenience" and check their sources. Maybe it is just a wide spread rumor.

@BradThomas "1,2,4 and 8 all divide into 8"? Could you explain the convenience with this property and tell me why 12 would be inconvenient? Thanks in advance!

I will not accept this as an answer. My question is why power-of-two is convenient, not why defacto standard is 8-bit. And the history behind 8-bit mentions 5, 6 and 7 bits being used for real reasons, while going from 7 to 8 is motivated with a "meh, why not". I got the feeling reading different sources power-of-two had more to it than compatibility to current systems. (In reality the 8-bit gave 7-bit character sets parity.) Word is a different thing where I do get the benefit of power-of-two sizes, i.e. shift can be used instead of mult in calculations.

@jameslarge Being a C/C++ programmer I think of the byte as the smallest addressable unit of memory. Does that help?