I've noticed that some tools come with rather short cords. Things like
small hand-held circular saws etc.

The reasoning, I suspect, is that it's better for you to accidentally
chop up an extension cord rather than the one hardwired to the saw!

There are other tools where an overly-long cord attached to the tool
gets in the way of normal operation. Soldering irons especially. In
cases like this it's better to have a short cord on the hand-held part
and a longer cord on a stationary base.

Don't forget voltage drop etc too as a reason to keep cords only as
long as necessary.

Tim.