"Frugal tip" - dilute your shampoo 1:1 with water

There are scores of frugal sites out there, where people submit what they consider to be frugal tips.
Many are good, I agree, but more often than not, I come across these kind of tips:

Dilute your shampoo/body wash/conditioner/dish liquid 1:1 with water

I have tried it too, and found the result unsatisfactory.

If you are already using only as much product as you need to get the job done, why would you need to dilute it, and what purpose does it serve?

This tip is good only when you have been frivolous, and you automatically take more product than you need for one use.