Why can’t they wish back Bardock and Gine?

[DragonBallFoodie]

I'm sorry but some people just have to stay dead, even in Dragon Ball.

This list includes Android 16, Grandpa Gohan, Raditz and Bardock and Gine.

[TobyS]

1. Their souls have almost certainly been recycled by now.
2. Goku doesn't know they aren't total bastards like Vegeta or Raditz. (Which is actually a cool tragic element to the Bardock Retcon.
3. Bardock is still alive having been snatched by Mira and Towa, and somewhere out there lost in time due to Xenoverse events if you see that as Canon.

If Xenoverse is canon, then so are DBFZ and the SDBH anime.

DBFZ could fit I suppose Xeno and Heroes seem to be mutually exclusive. Unless you are just talking about Ult mission only.

[Yedis]

Its been 30+ years since they've died. Goku would probably be older than his parents if they were revived. I don't think they want to introduce that dynamic to the audience.

[Daisetsu]

Goku barely knew them and has no memory of them or any connection to them at all.

What do you mean “recycled”? As far as i remember, there was never a time limit to how long a person could be dead before they’re unable to be wished back.

The cycle of reincarnation. Their souls are purified, stripped of their memories and reincarnated as someone else.

When was it established that all dead people get reincarnated?

Way back in the Buu arc, just before Vegeta sacrifices himself. Although, it's not really ALL dead people but just those that don't go to heaven (Kaio notwithstanding). Piccolo explained that the souls that go down to hell get cleansed and reincarnated as new life and, as recently revealed by Toriyama, some souls take a lot of time to be cleansed based on how evil they are. I have no doubt that Bardock was sent to hell and has likely already been reincarnated and Gine was most likely sent down, too.