Actually, I remember in some model of Lenovo Thinkpad (like the T450s) the BIOS settings has exactly such a setting.
My Thinkpad X260 has
exactly that option in its BIOS. I consider it a huge advantage. It allows you to make a USB connector a source of power even if the laptop is
completely powered down. Combined with its dual batteries (internal and externally swappable) it's incredibly useful.
This is my first ThinkPad, but seriously it's the ultimate Road Engineer machine. Natively runs Win7 (a personal requirement). Has all the standard ports (rather than requiring USB dongles for everything) so I can natively connect to Ethernet, USB, video, etc. The internal battery keeps it running while you hot-swap the regular battery, and with both batteries charged you get an easy 16-20 hours of normal use. Carry a spare battery and you can get a full 8-10 hour workday while letting it power external devices like programmers, debuggers, and (presumably) USB tools like a scope. It's got an i7+32GB+SSD so plenty of computational grunt, and while it doesn't have hardware graphics acceleration it's been plenty fast for everything except live Premiere Pro editing.
Standard disclaimers, no association, etc. It's not paper-thin like the latest museum flagship laptops but it runs twice as long and is at least twice as flexible.