For me it was not do much a choice.

I started out using basic and simple text display (graphics existed but was quite difficult).

For a long time I was the sole or part of a pair of devs so specializing was not possible and once we grew to such a size I already was quite proficient in all areas from hardware to customer support and education.

But from that time onto today I have gravitated towards a more backend role mainly because I lack a good sense or visual design.

I know it something looks good, but doing it my self results in more boring or plain designs where more thought goes into UX than nice looking design.

That said, if we do web applications I can still keep up since it usually is more ux heavy ;)

But when it comes to adding background images, nice color sets and such I gladly defer that to colleagues with a better design sense.