This topic just won’t die …
A good rule of thumb is to “adjust” your sketching prowess as a function of the interviewer. Remember design consultancies, for the most part, live off selling their clients concept proposals, and many of them! Conclusion: you must excel at finished presentation-level renderings in all media to be hired. In my (early) experience interviewing at design offices they all talk endlessly about the importance of concept development sketches showing process but still end up hiring based on flash, and less on substance.
Things change dramatically in corporate design offices and manufacturing where, believe it or not, they actually expect to make and sell the fruits of your passionate sketches. What primarily matters here is that one elusive concept their clients will buy. Whether it’s experienced designers, engineers or corporate types peeking at your worth, solid ideas translateable into sales take front stage. Sketching is seen as a PERSONAL skill for refining your own thought process and output, but it’s not like the VP of Operations, Accounting or the mold technicians give a s–t about the framed renderings on your office walls. End results count above how you got there.
Design consulting firms in some ways (unfortunately) pursue on the design school approach of emphasizing the craft of good design over its more pragmatic, less glamorous market impact. Certainly, if they make a living at volume-selling paper concepts, you’re expected to draw like the Old Masters from the moment your pen hits the paper, that is from the most basic sketch to final renderings. It’s what their own clients BUY.
I for one, am more interested in a designer’s sensibility and intelect, less so sketch, modeling or other craft skills. These are a bonus, but where I work, never a necessity affecting a project’s final outcome.
Don’t get too precious and self-conscious about any form of hand drawing, that is immediately visible to an experienced eye and can really sink an interview. It remains up to you to decide on which particular skills you’ll be selling yourself on. Leonardo Da Vinci-types are usually one every several hundred years or so. Don’t make claims you cannot support.
If so many firms hire on sketching skills it may be they are themselves short on real-life hiring criteria that count, not to mention short on ideas in general. Asking new graduates to shine in all categories is not only unrealistic, but downright abusive. I’d always hire a professional product illustrator (an artist) separately from a designer.
But then, some people would rather keep squeezing a dry lemon than buying a new one. For years now, the oversupply of ID graduates has made sure these hiring practices will not change anytime soon.