Many times this option is the best option, but it's not the best available option. This is because of a lack of trust. People are worried they are going to be r

Many times this option is the best option, but it's not the best available option. This is because of a lack of trust. People are worried they are going to be ripped off, so at least want some proof that a given number of hours that seems reasonable was expended and then they check that a reasonable rate was charged per hour, and it makes them feel more confident. These people are often very frustrating to work with.