A bit of a generalisation but there are opportunists and “pro” thieves. Opportunists will nick anything if they get the chance, doesn’t matter how old or ratty. If they get a tenner for it from a low level dealer to get to his clients on then they’re happy. They’ll carry cable cutters and/or shorter bolt croppers, concealable and quick. Cable cutters will do for cable locks in seconds, probably quicker than using a key. Croppers can defeat cheap crappy d locks and thin chains especially if locked close to the ground where they can brace one handle on the ground and use body weight.
Pros are the ones using the grinders and targeting more expensive bikes. You can put off most of the opportunists with a decent lock, there’ll often be another bike with a cable lock but to avoid being targeted by the pros you need to lower your risk profile, being careful of where, when and for how long you lock the bike.
Agreed - but there is an extra type of opportunist
the genuine opportunist who is wandering about with no intention of knicking a bike but if the chance come up they will go for it
It might be a simple as being an easier way to get home where they will dump it - possibly by the side of the road - possibly in a canal!
These people - in my opinion - are the majority in areas with few bikes but they don;t carry any specific tools.
Hence they are after something easy and quick that requires little or no effort
And they often don't know one bike from another - maybe recognise some of the more expensive but common bits but not much
On my High Street there are often several bike just parked up with no apparently chains/locks or anything - and yet they don't get knicked much as far as I know. OK - they are normally rubbish bike - but they work.
There are also bikes locked up with cheap Pond Shop/supermarket cable locks - any decent cutters would go through them in a second - but again they seem to stay there
In these circumstances locking my ebike up with a "no too bad" cable lock though the wheels and a D-Lock round the frame and cycle stand is probably OK - especially if I take the battery!
But I still have it insured and check the insurance security requirements every year!