Is having all locks with the same key a bad idea?
If you lose the keys, or need to give them to someone who you later come to distrust, or post a picture of them on the internet then you'll need to change both locks instead of just one.

If this is just two doors, then it's not really a big deal - slightly more inconvenient if things go wrong weighed against slightly more convenience in everyday life.

(Note that a 'lost keys' insurance policy may not pay out to have both locks changed if you lose the keys - it's a conversation you'd need to have with the insurer prior to purchasing the policy.)