While that is a very common use case (bootp), I’ve ran across a lot of hardware that use it for config upload and download:
To upload a config to an industrial grade Garettcom switch you need to use tftp. Same goes for firmware updates and config backups.
This Cisco phone I was battling with once tried to download a config vea TFTP feom its DHCP server, assuming its DHCP server was part of the SIP infrastructure. The above mechanism was also used successfully by some other proprietary hardware built inhouse for firmware updates.