Saint evil: It would help if you recorded your flying experience in your profile. Then we would have a better perspective on where you come from.
In its absence, I would hazard a guess that you aren't a regular civvy operator (commercial or otherwise).
You would understand where Crab is coming from, appreciate that it sounds commonsense, but then realise that IN REALITY, based on realistic local air traffic pressures, and the fact that it is not MANDATORY (I wonder why), that 121x5 on constant listen out is not derigeur.
It would be ideal to monitor it all the time, but as I have just witnessed today in Snowdonia:
All my transmissions on 121x5 were met by a loud silence.
The national park was swimming in FW and light helo's [5 of them at one time] and they were all listening out on caernarfon and Valley - where the action was.
Now do they deselect one of these to listen to 121x5?
It's all down to risk management and thats what piloting is all about.
If my colleagues at the air ambulance and myself did TDA's today for every job we attended in the parks, the whole area would be an avoid until just 10 mins ago.
Get real, stop being a prat and join the real world.