UUIDs rarely have to be unique compared to every other place in the world where they are used, they just need to be unique within the same context. The reason for using NIC addresses and time is to ensure that the chance of a collision is really small (but not 0). Saying that you are making them a little more unique doesn't sound like good motivation.
The second part is that just using random numbers gives you no real guarantees of uniqueness since without seeding with time and NIC, it would be highly likely that multiple systems around the world would generate the same number.
"Highly likely"? No. You are ignoring probability. See UUIDv4, which does not use time or NIC/MAC but does use 122 random bits.
https://zelark.github.io/nano-id-cc/
At the default 64 character alphabet with a 21 character key length it would take ~41 million years in order to have a 1% probability of at least one collision if you generated 1000 ids per second.