Print designers coming to the web, often have problems with this. Using fonts that won't render clearly, justifying columns, tiny gray text on white, a background that stops repeating after 1600px (the size of their monitor). Fixed width designs wider than 1200pixels. Very uneconomic gradients.

For someone who calls herself/himself a web designer these problems should be non-existent. If you don't know the medium for which you design and its limitations, you are making a flyer in Photoshop, not a webdesign.

Beautiful functional web design follows from real content and interacting with the page like a user. A web designer who doesn't venture beyond Photoshop will likely produce very one-dimensional designs.

A front-end developer should know a lot about design. Not as a suggestion, but as a given. To do a design justice, you have to translate it with care. I see the need for overlap more for back-end developers and front-end developers. Back-end needs to understand valid HTML and front-end needs to work with a template engine and do data requests.

For web designers and front end engineers, a full overlap should be a given, and it isn't that rare to find one who can do both. Now back-end vs. web design is a chasm too wide to cross, realistically.

Why is that?

I have worked professionally as both a designer and developer, and find many parallels between two. In my opinion, my very best programming work has been code built from my interface designs. The design process allows me to have an intimate understanding of the application flow before I write a single line of code. I find working from the designs of others never allows that same level of understanding, leading to a codebase that takes longer to make great (which, in business speak: longer = more expensive).

Thinking back, I started on my path to designer at around the age of five, and started learning to program around the age of ten, so I have a lot of experience in both fields. Perhaps someone who doesn't start until college simply doesn't have enough time to become proficient in both?

I think people want to be good at what they do. The best designers can either "waste time" on becoming novice programmers, or they can perfect their core craft. If they spread too thin, they might soon stop becoming the best.

I guess it also depends on the role you play in a company or start-up. If you can help out other teams and communicate, that is very useful for a start-up or small business, but not something I think is appreciated in some larger companies: You get judged and hired on one core role and are expected to do that very well. If a big company needs design, they likely hire a full-time designer, not ask that DBA with a keen eye.

I am sure there are a few hack-of-all-trades that mastered full webstack programming, data analysis, community management, marketing, SEO, usability, copy-writing, design etc.. But I also feel it is unrealistic to expect one to be able to switch to the other, regardless of their individual talents and expertise.

I remain skeptical of that. Perhaps my brain is just mis-wired, but I find that there is no real divide. What I do find sometimes is that my ability on each side comes and go in waves. That turns out to be the perfect fit for software development: When I struggle with logic problems, I can jump and work on the design problems and vice verse. That way I can stay at peak performance all the time.

And about what you said about print designers coming to the web, I think the problem is that _design_ (as probably everything else) is context dependent. If you are good at designing print pages it doesn't follows that you automagically be good at web page design. There is so much to learn from the trade.

You have to develop your design skills in every new area that you intend to work on. I think you can get a hand from your previous experience to ease the experience, but there is no saving from having to learn the ropes, even if it is only for a little time.