Yeah, go ahead and pack your bag. I hated this recommendation when I got it but it did make life easier -- pack nursing gowns and don't really worry about pants (except maybe a couple pairs of yoga/sweat pants). Nurses are going to come in every few hours and check your underwear (yup) so pants are a HUGE pita in the hospital.
Also, DON'T FORGET YOUR PILLOW! My hospital had plenty of their little disposable ones but they said they're often running low and sometimes don't have enough for everyone. I found my own pillow to be a lot more comfortable than theirs
And cell phone charger.
And toothbrush/toothpaste.
Other than that, I packed way too much last time. I kept reading how you're going to want to use your own towels and your own bath stuff and your own fluffy socks and your own underwear... whatever. Not the case at all for me so I'm not packing any of that crap this time. 1) Yes, hospital towels suck. But I don't want to get blood all over my own towels, so I'll use theirs. 2) I only took one shower in the hospital and I used the shower gel & poof they gave me. I was too tired to bother the night after she was born so it didn't happen until the afternoon after when they were going to force me to be present in front of other people in the discharge class.
I honestly was afraid of showering my lady bits
3) No, I never wore my own socks. The hospital gave me socks and I'd prefer to keep my own socks free of amniotic fluid and blood. 4) Nope, not for me, big net one-size-fits-all hospital underwear FOR THE WIN for the first couple of days! After that, my own huge cotton granny panties were fine but I won't bother packing more than a couple this time. I packed like 10 last time because I kept reading that I'd be more comfortable with them and that I'd want to change them every time I bled on them and... whatever. Maybe it's just me, but I straight up didn't give a flying crap about my underwear the first couple of days.
I also packed a ton of snack foods and drinks. I won't be doing that again. The hospital gave me so much food I thought I was going to die trying to poop it all back out.
I also packed too much for baby last time.
I don't know, maybe my hospital is just generous or something but I ended up packing way too much crap going by the hospital lists I had found on other sites.
I guess better safe than sorry if you don't know what the hospital will provide.