I've cycled on and off for the past few years to Shoreditch. Reasons why people might not cycle, based on my journey:

I'd imagine if like me you have no shower at work, you need a Gym membership or something to have a shower at work.

As mentioned above, especially in the summer, London Bridge cyclists are a nightmare, both in terms of number and general cycling attitude.

On my journey I've had buses regularly pull out in front of me, taxis stop at no notice and one person to decide when stuck in traffic to get our of the cab right in front of the bike. The concerned taxi driver came over to check his door.

I've also (entirely my fault) come off my bike in a park and broken my arm.

Cycling up Honor Oak Road fro Peckham Rye is something I am never going to enjoy, especially the last bit!

That said I still generally enjoy it. I don't find it faster but about the same, on a good day with the traffic lights going my way I can do it in 30 minutes door to door, that is on mainly main roads (I go on the A2 now) but I then need to shower, get changed etc at a gym 10 minutes walk from the office.

I do feel better when I get into work and it is of course good for you. Despite what I wrote above, I find it generally safe if you keep your wits about you.