We allow people to use their own tools, but I do find there is an advantage with standardizing them. If a truck has an issue, it is easy to switch to a different one,
if every guy uses the same brand of power tools it is less trouble and cheaper to manage batteries and less likely of it being an issue.

you know what I find ironic in this statement? it appears as if you care if the employee "won't respect and will destroy" your 2$ screw driver but you don't care if he "won't respect and will destroy " the customers priceless one of a kind vase. The way I see it that 2$ screw driver is easily replaceable, but anything that goes wrong in an install can cost me millions (in lost future jobs) so why would I want an employee that does not respect something just because he did not pay for it.