can't/couldn't + perfect infinitive

  1. the conversation between two persons:
    one person:He returned home with a tiger club.
    second person: Hi wife can’t have been very pleased about that.

why can’t we also say:…couldn’t have been very pleased…?

2.the conversation between two persons:
one person: He was very sick last night.
second person: The meat we had for supper can’t have been good.

why can’t we also say: …couldn’t have been good?

  1. what is the difference between for example: ‘can’t have been’ and ‘couldn’t have been’? when should we use each of them?

Thank you very much.

You can also say “couldn’t” in both cases. There is little difference in these examples. I suppose “couldn’t” feels slightly more removed and hypothetical.

Did you mean “tiger cub”?

yes, a tiger cub.
Thank you Dozy