Because it’s an inefficient use of time and money. All that you’ll achieve is less people cycling and that’s exactly the opposite of what you want. Think about the practicality of a cycle license: do you expect a 6 year old to pass a test before cycling? A ten year old to carry along a license when he goes out? You can’t even fine them because the statuary limit in germany is 14. You can’t fine the parents either because parents are not obliged to keep their kids in sight all the time. Adults are already very likely to have a drivers license, should they now need a cycling license on top.

So make better use of the time and money: create safe infrastructure or - as a better investment train those that already have a license requirement and that insist on moving around tons of steel. Maybe increase the number of hours in school that deal with safe conduct in traffic. Or - gasp - fine the people blocking cycle lanes and otherwise endangering cyclist hard.

So the conclusion here is that cycling is fine just how it is, based on a cost/benefit analysis, and that motor car users need to be regularly examined and educated to ensure good road safety for everyone?

no, that's not the conclusion. I didn't bring up the "let's have a license requirement for cyclists idea." My point is that this is not a change that would improve cycling in a way that outweighs the negative effects. It's a bullshit idea that gets floated from time to time.

Improve cycling by all means, but use something that is effective: better infrastructure, education, enforcement. The Berlin police introduced a police squad on cycles a few years ago in one district and that has proven to be a very effective method: For one, they enforce road rules for people on bicyclist, but the major effect is that they remove cars from infrastructure dedicated to bicycles which in turn actually enables cyclists to use that infrastructure and makes people less likely to ride on the sidewalk, for example.

Education is generally far more cost efficient than building new infrastructure like roads.

No, not in this case. It's not like people don't know the rules and the majority of people get killed despite being absolutely in the right and having done nothing wrong. How do you fix that with education? The dooring accident that nearly killed me happened on a cycle lane that I was by law required to use. The car driver just opened the door into the oncoming cycle traffic. How could you educate me better in a way that would have prevented me from making a hard impact with that door? Witnesses told me they didn't even expect me to get up again. How would educating me help prevent the three close passes I had today, especially the one where the car driver thought I'd have to squeeze into the dooring zone? The one that passed me when I was doing 30 in a max 30 zone? The close pass yesterday where the car driver didn't manage to pass me before the oncoming traffic was there, squeezing me against the parked cars? I was in the right, still I'd be the one dead. Should I yield and crawl? Cycling isn't a sport for me, it's my preferred mode of transport, I really want to get somewhere and I don't want to spend ages doing so.

Calling for education of cyclists has a strong smell of victim blaming. Oh, sorry, he's dead. If he'd been better educated, he might have known that he was in the right.