[tialaramex]

They didn't explicitly deprecate TLS-SRP, it simply can't work in TLS 1.3 because although it superficially looks like a minor revision, and indeed (to defeat middlebox ossification) on the wire it appears to say it is only TLS 1.2 in reality it's a fairly radical change.

TLS-SRP bolts over the traditional TLS key exchange mechanism, which made sense, but in TLS 1.3 that entire mechanism is gone, keys are either pre-shared or they're always agreed in the first protocol burst using an (elliptic curve) Diffie Hellman method. So by the time you'd have a natural opportunity to do SRP the protocol has already agreed keys anyway.