Why do people leave filing their tax returns to the last minute?

As we approach the 31 January filing deadline for filing personal self assessment tax returns, I asked a few taxpayers why they leave things to the last minute. A selection of their replies follows: 

Flights to Panama are cheaper in January. 

I've made HMRC my best and only deal available. It's their choice to either accept it, walk away, or it's no deal.

Fear of figures 

My girlfriend said she'd do it for me 

HMRC = Hold Money Past Christmas, I Have Many Reliefs to Claim or Hope My Rebate Comes 

I know exactly when the last minute is. The first minute though...? 

If it wasn't for the last minute I'd never get anything done. 

I've got plenty of time as the last minute isn't due for another 4 or 5 billion years.