Where is this information coming from?

I've received large (not $10k) vouchers from major airlines before, and the only restriction is the expiration date.

They are effectively the same as cash for that airline, and I have yet to see a VDB voucher that is significantly restricted.

Airlines do give away a lot of "good will" certificates during irrops (e.g. weather events) to upset customers, which function more like coupons than traditional vouchers.

I'm happy to be proven wrong, but checking with a few friends who between us fly all the major US carriers - VDB vouchers are effectively airline cash with an expiration date.

Like the other reply you got, I've received a multi-thousand (but not $10k) voucher from United before and the only restriction was use within a year. I also didn't have to use on a single flight, but could use the full value on one flight if I wished (which I did, flew paid business, but was upgraded to first to APAC).

Ugh, please don't make unfounded claims like that.