Security is a joke everywhere you go, the alternative is a Police State.
Fact:- blowing things, people, planes up is easy
The reason it doesn't happen every day is because it would lose its impact in the same way we couldn't give two hoots when we see dead people on the TV.
The IRA had 20 years of doing evil things but in the end you just waited for it to happen and got on with life. No big deal if you weren't hit and if you were then you had your 15 mins and no one cared after that.
If things start getting past "buggeration factor" then we'll see some action but, in our "civilised" society, it is unlikely to amount to much.
Bottom line: get used to it. Security will be what it needs to be to prevent student bombers with nothing better to do but will never be more than mildly effective against groups with funding and a cause that they're willing to die for.
As stated, a firework every so often gets much more attention then every firework in a display and that's what keeps us "statisically" safe.