Why do all kettles have a 1.7L capacity?

Chris Smith posed the question to Andrew Morris.

Andrew - I was forced to do some research on this and Googled around, and he's quite right; almost all kettles are 1.7 litres. So I made an inquiry with the Bosch research department, and basically, as your listener guessed, it's the nearest equivalent to three pints, which is apparently six standard cup fulls, which is apparently the standard size of a teapot.

Chris - A teapot is an SI measure, is it?

Andrew - So apparently the kettle fits the teapot standard. I'm afraid there's not a lot of physics in that.