Well, in my particular case, if it was in a game that was a homebrew, they wouldn't really be engaged in an adventure I wrote, because I don't do that. I tend to create situations and have PCs do whatever they want and do my best to respond with fun and internally consistent material. So if they TPK, they are just one more group of would be heroes mouldering at the bottom of a kobold pit (or whatever) in a broader world full of such stories.Why?
So, you have a group of players - they are engaged with an adventure you bought. All the PCs die.
Contrast with the same group of players - they are engaged with an adventure you made up. All the PCs die.
Why does one have more consequences than the other? I mean, they're all dead, either way, right? Is there some other meaningful consequence here?
Again, this is personal bias, but when I am running a big fat zero-to-hero module, it doesn't feel like that. They are the stars of Descent into Avernus and so them failing has much larger repercussions for the game.