As a committed listener to music while cycling, the OP rang alarm bells because they seemed to be wanting to be cut off from the outside world.
Having music playing has always made physical exertion by this totally non-sporty person that much easier and eased me into actually improving my fitness. The fittest I ever got was pounding the boards at the local rave-type events in my late 30s (wearing earplugs and staying away from the speakers).
So in 26 years and over 40,000 miles of cycling I have never set out without music - unless I'm on a group ride.
I find it difficult to separate shoes, gloves (I never ride without full gloves) and music as essentials. Wearing a helmet comes second. Were it to become illegal, I would start breaking the law for the first time. That applies to helmets as well - even though I had my first fall involving concussion a few years back (I was wearing a helmet). Since then, I greatly upped my game where bike maintenance is concerned and deliberately don't wear one on weekend rides.
(I mention the dreaded "H" word because I think it's related)
When I first started cycling - after 10 years as a motorcyclist, I was purely a commuter, a large chunk of my commute is on a converted railway path, and the suburban roads I still use are very quiet - and since the madness of the school run got properly under way, I've re-engineered my routes so I see even less traffic.
I have over the past few years sometimes doubled or tripled my mileage - still on shared paths and country roads - mostly on a Sunday - though clearly that isn't always possible - but I have to confess I have no experience of cycling through miles of city traffic during the rush hour. Doing this vicariously through watching cycle-cam videos makes me wonder if I could actually do it.
I only briefly tried listening to music on my motorcycle - the crash helmet and the engine noise means you're already cut off from the real world - quite frankly I've lost my nerve where ever getting on a motorcycle again is concerned.
Whenever I'm obliged to drive a car, I'll open all the windows - - whatever the time of year - or I feel too cut off from the world while driving such a potentially dangerous vehicle - what else is all that waste heat from the engine going to be used for ? I will listen to music to make it less of an ordeal.
So do I take my safety on a bicycle too lightly ?
Certainly when I started riding 36 years ago, I remember "relying" on the crackle of my FM radio to tell me about cars that got near.. and I remember playing the music loud and singing along ...
I only once tried in-ear phones - I think I lasted about half a mile... being so cut-off gave me claustrophobia - so I've always chosen "leaky" on-ear phones - and my current ones are so leaky that sometimes I have to untangle the mostly electronic / ambient music from the real world - but I do occasionally gain some advantage from hearing vehicles approaching - though not to the extent that I consider I'm taking unnecessary risks. And clearly on busy roads, I may even take the earphones off.
My afore-mentioned experience with "repetitive beats" in the late 90s changed the sort of music I listen to and the way I listen to it - and I'm also these days much more engaged with my cycling.
So it's a mixed bag. It depends on the rider and the road conditions ... morally we start on higher ground because it's about our own safety whereas cars are inherently dangerous and coincidentally cut the driver off from their surroundings - which air conditioning must surely have made even worse - add the distractions of passengers and gawd 'elp us, mobile phones ...
) into a slight breeze and I noticed/thought about wind noise and did some experiments. Moving my head at different angles changed the wind noise dramatically, and making a little 'fairing' ahead of my ear using my fingers seemed to reduce it considerably.
as much utilised by sound recorderists.
