As I see it there are two questions in this thread,
“Is it okay to leave your bags unattended?” and
“Has the terrorist threat on the rail network been wildly exaggerated?”, and I would answer both questions with a guarded ”Yes”.
On the first question, I’m with the OP; it’s perfectly acceptable to stay a few feet away from your bags when on a platform,
so long as your bags remain within your own view. This is of course mainly so you make sure your luggage doesn’t get nicked rather than anything to do with suspicious packages but it does mean that if some over-zealous member of platform staff tries to interfere with your bags, you can immediately go over and stop them. I also found it amusing that someone suggested that you shouldn’t wear headphones on a station as you won’t hear any security announcements – the reason why most of us do wear headphones is that we don’t have to listen to the constant barrage of unnecessary security announcements in the first place!
The second point is that, without any evidence to the contrary, it’s logical to conclude that the actual terrorist threat on the rail network is much lower than the security services would have us believe. When this subject came up on here a few months back, a google search revealed that the security services had prevented a mere 13 attacks in 4 years (in the UK as a whole, not just the rail network). (
http://www.bbc.co.uk/news/uk-39176110 ) and, as already mentioned, the last terrorist attack on the rail network was 24 years ago. Even this list is open to conjecture; no proof or details have been published. In order to believe such figures I would expect the security services to tell us who was behind the attacks and when and where were they going to occur, to hide behind the flimsy
“there’s lots of terrorists planning to kill us but we can’t tell you about them for security reasons” is simply unacceptable and in the absence of proof how can they be believed? It is of course in both MI5 and the governemnt's interests to scare us unnecessarily as this justifies giving the security services extra funding and also a scared population is likely to be far more obedient and willing to accept greater restrictions on their freedom but that's another argument for another thread.
Whilst if you live in London, it might be understandable for you to believe the terrorist threat is “severe”, when I’m waiting on a country station platform in rural Yorkshire, the chances of me being a victim of a terror attack are, as they have been for years, somewhere between “pretty remote” and “non-existent”!