Here's my finger in the air take on it...
I cycled regularly on road from around 1980 to 1996. Had something of a hiatus for a good few years, mainly due to where my bikes were stored, when I only very occasionally got the chance to cycle.
In recent years I've had more opportunity to use my bikes, although it's only really occasional use. But the thing I've found about cycling these days, on road, is that the roads are nothing like as friendly as they were to cycle on in the past. That's both in terms of road layout ("traffic calming") reduction in width of lanes (and the consequential effect that has on drivers' demeanor), plus increasing numbers of vehicles - and it does have to be said, driver attitude.
I do personally feel like the roads are more hazardous to cycle on. In recent years, I have looked forward to having more opportunity to cycle, but practically every time I cycle somewhere on road, I find either aggressive attitudes from drivers (in terms of their actual driving behaviour, or any interaction) and / or loutish behaviour from either drivers or passenger. Now sure, societal attitudes and trends play a big part in that - but also, road designers can't distance themselves from cause and effect, either.
I think, nowadays, I'm less inclined to cycle with traffic and prefer to cycle on paths or tracks without vehicles (I'm not thinking of cycle paths on or by roads, there, though) - and I'm not the timid or shy and retiring type. I just find that my recent experience of cycling with traffic tends towards it being a generally negative experience for me, and if I'm doing something for enjoyment, why put myself through a part of it which is far from it, these days.
Now don't get me wrong - I don't perceive that as being a good thing for me - to be perfectly honest, recent on-road experience notwithstanding, I've tended to long for the days when I did practically all my commuting and moving around by bike. But times have changed, as I believe the roads and drivers have.