Why the increase? Thoughts:

1) Easier and quicker to push options (20/30/40%) than key in lower amount.

2) Pre set options may lead to mistakes.

3) Customer doesn't want to embarrass themselves by entering an anoint so just pushes a button.

4) The average fare and average cash in hand leads to per tips versus card payment. Eg Avg fare $9 and most payments with a $10 note.

5) Customers willing to tip higher due to preference towards card payments.

6) Peak in typing due to early adopters using technology.