Is this really a problem in practice?
Only if you use a very, very shitty wallet. I remember reading
this case (although it was about "R values" instead of "nonce k").
blockchain.info is probably the most popular shitty wallet in short bitcoin history! I remember at some point they were using random.org to generate k value! And they even did that in the stupidest way possible. The code didn't even check if the http respond was successful or sent the correct reply; so when random.org changed its system and started sending a broken respond, the blockchain.info wallet software used that as the actual respond and computed k value based on that so everyone using their wallet ended up with the same k value!