I don't think your red chair analogy is very strong to be honest.
First off, if the chair has a counter attached which will cause it to explode when the millionth person sits on it, then that's different to a chair which has 1 in a million chance of exploding. A chair with a 1 in a million chance of exploding may never explode, a chair which explodes when the millionth person sits on it is an inevitability.
Further, a 1 in a million chance is not just slim, it's irrelevant. No rationale person would changed their behaviour on a one in a million chance, let alone the vastly smaller chances of getting blown up on the tube.
Tube journeys per day 2,670,000
Days since 07/07 396
Tube journeys since 07/07 1,057,320,000
Deaths BT 52
Injuries BT 700
% Deaths on 07/07 0.0019%
% Injuries on 07/07 0.0262%
% Deaths since 07/07 0.000005%
% Injuries since 07/07 0.000066%
By way of comparison, your chances of dying by falling out of bed are 1 in 2,000,000. You have a one in 685,000 chance of drowning in your bath. You have a 1 in 43,500 chance of being killed in a work related accident. Chances of dying in a road accident? 1 in 8,000.
Are you going to stop getting out of bed? More likely than getting blown up on the tube.
Are you going to stop bathing? More dangerous than travelling on the tube.
Etc.
Personally, I'm not going to get too upset about the one in 20,333,077 chance of being killed on the tube.