Maybe it's just our phone interviews that allow us to focus on higher-level concepts in person, but I've really never found a candidate who did poorly on a whiteboard but seems like they would have done well on a computer. If anything, it's the inverse where candidates jump straight into code, to their own detriment, when placed in front of a keyboard.
Now while you may be aware of this and not give the candidate a hard time for not leaving enough space, I read a Medium post once written by a Google employee with tips on doing well on the interview. He explicitly highlighted this problem, and literally encouraged candidates to learn to think and write linearly and not leave these kinds of blank spaces.
* IT just fails: they’re unwilling to supply it, there aren’t enough, the current laptops on hand are junk, or the default password is wrong. These all happen with HR buy-in and funding.
* Recruiting just fails: they “have to move the candidate fast because of a competing offer,” they tried to work with IT but IT blocked them, they got laptops themself using their own budget but then ran out.
* I failed: I didn’t make time to prepare a non-whiteboard question, I didn’t tell my manager in each and every 1:1 that candidate experience sucks, I had three laptops and I forgot to bring my personal spare to the interview.
In general the core problem is there is zero incentive for hiring managers to do anything but shotgun candidate pools like they do today. There’s also no feedback loop to evaluators to help them improve. False negatives are completely tolerated despite there being a huge gap between CS jobs demand and CS graduate supply.
All these companies expect you to write code using a site like hackerrank during the phone screen. And yet they can't have a chromebook open to the exact same site during the onsite? If that's too much, they can't even get a cheap laptop, stick in a USB drive linux distro, open nano and give that during the onsite?
I think this is the bad assumption that's causing your confusion. Maybe this happens, but I think it's very uncommon.
The point of using whiteboards is to focus more on algorithms, data structures, and problem solving, not just spitting out code. If you make the applicant write actual code it limits the scope of the questions that can be asked.
So, it's actually beneficial that whiteboards aren't good for writing compilable code, because that's not what you want the applicant to do.
However, a whiteboard certainly can be easier to write anything that is not code on. Like for instance if the candidate chooses to walk the interviewer through a high-level approach, including a graph topology, before actually starting to code.
I know Google started letting candidates choose between laptop and whiteboard a few years back. I suspect others alos have.
I'm not including a compiler or having build tools or an IDE. Just a basic simple text editing area that allows the basic functions of typing in text and editing it.
I'm against these leetcode interviews. But if you did nothing else but change this one thing, just stop expecting people to write code on a whiteboard or paper/pencil and allow them to write code the way it's actually done (a computing device with a keyboard and text edit area), that would be such a huge improvement. Writing code on a whiteboard or paper doesn't test anything. Think about how limited it is and how different it is (for example, you can't just press an up arrow and add a newline, have to find an eraser and start over).
It's yet another useless skill to learn just for interviews (writing compilable code on a whiteboard/paper) which also encourages rote memorization (because you have to get it right on the first try since editing the text is so painful and difficult).
I hope people start pushing back on this. The reaction should be, wow you care so little about your interview process that you can't get a $200 chromebook in here?