Imagine a telling a group of obese people "Those people who have not gone on a diet in the last 4 weeks are not overweight because they don't want to be slim".
"Anyone who has not had an address in 4 weeks is not homeless because they do not desire a home".
You can probably imagine hundreds more scenarios. When faced with repeated failure, many people fail to act in their own interests. In fact, I don't think the unemployment number is necessarily dumb -- it measures the number of unemployed people who have not given up hope of working. But we really need a measure of all the people who have given up hope, but still want to work.
What's unfortunate is the attitude that your question implies (and I'm not actually suggesting that you have this attitude, though it is very common): it is easy to think that people who have given up want the failure that they now experience. Normally this is not the case.
I once saw a homeless person trying to explain to someone their predicament. I don't remember their exact words, but it was something like this: "It's -5 degrees C today. I live in a cardboard box on the side walk. Do you really think that I wouldn't rather sleep in a warm bed? But I've got a lot of problems and this is the best that I can do right now." Followed by considerable profanity (probably their case would have been easier to follow for the listener had that been omitted).
I don't think it's connected to insurance benefits. I think the statistic is dumb, because it should count people who are available to work but aren't.
On the other hand, if you aren't looking, maybe you really aren't available.
If your collecting benefits your filing a report stating that you are/looking & available, if your not collecting EI benefits, your not filing report, your likely not counted as "officially unemployed".
You may fall into the broader U6 unemployment numbers that u/roofus mentions below.
Of course, I doubt both show underemployment.
Came across an interesting article[0] about how they are measuring these along with some historical data. It touches on underemployment as well, indicating that the underemployed are included in the U6 numbers.
The articles most recent(2015-06) monthly U3 rate of 5.3% is about half of the U6 rate of 10.5% for the same period.
[0] http://econbrowser.com/archives/2015/07/measuring-unemployme...