copy?

I know, I know, who uses discs, who uses a library???

I can only seem to find Bob's Burgers seasons on DVD, not blu ray. So I thought I'd check out the DVDs from the library to see if the quality is good enough (I feel like animation on a DVD is sometimes good enough on a 4k TV). The part of the DVD that has the data is purple and clearly a burnt disc, not a stamped disc (it's called stamping, right? like a record?).

Why would the library have pirated copies of stuff to check out...?