The way I see it, it's just about having the will to
enforce it.
After all, seat belts did not come with the first car. They were
only invented later on, and were made compulsory even later still.
I'm pretty sure that drivers were at first highly resistant to the
wearing of seat belts until the authorities pursued it
aggressively.
On a similar note, I'm sure we can institute some form of
Rider's Education lessons or something in secondary schools, make
everyone take Basic Theory at the end of Sec 2, then give all those
who pass a licence to cycle on roads. The Traffic Police can be
given the mandate to aggressively go after cyclists who break
traffic rules.
So really, I think it's just a matter of having the will to do
all that.
Don't forget about migrant workers who cycle on secondhand bikes
too. How does one make this accessible to them?
Another point - there are some cyclists who do it to get around,
and others who do it to keep fit. Of this latter group, some ride
like maniacs and hate to stop. Fatigue is always a danger when
you're in traffic.