I ported around 20 RNGs to C# (all non-cs), and there are tons of uses for non-cryptographic RNGs, so I'm a little torn. I guess in modern development most people who need an RNG need it for crypto purposes (I would guess salts, keys and nonces mostly), but I'd hate to see all the Xoshiros, Mersenne Twisters, PCGs, and MWCs, etc. go the way of the dodo simply because they are not deemed fit for crypto purposes. Games, simulations, non-cryptographic hashes all need deterministic and high performance RNGs, and don't need all of the cryptographic guarantees.
To top it off, there is no standard definition of what makes an RNG cryptographically secure, so it's a slightly loaded question anyway. Everything I've read says an algo needs the following properties: forward secrecy (unable to guess future outputs given the current state), backward secrecy (if I know current outputs, I shouldn't be able to recover previous internal state or previous outputs), and the output must be indistinguishable from true random bits, even with a chosen-input attack. This is where I politely defer to the expert mathematicians and cryptographers, because I'm not equipped to perform such an analysis.
I can understand why things have developed this way though- people have needed random numbers far longer than they've needed cryptographically secure random numbers, so the default is the non-cryptographically secure variant. A language created tomorrow would likely follow in Go's footsteps and default to the cryptographically secure.