Not at all, lots of people already live together and have everything they need, there'd be no point getting 5 more toasters. Plus it makes the gift giving easier, I prefer giving a card with money to a newly wed couple because I know they will use it to get something they want.
No, I understand perfectly that having 5 toasters is silly, but that's what wedding registries are for, and of course, anyone is free to give money if they so choose.
And it's okay to personally ask close friends and family for money instead of a gift, but putting it on your invitation is distasteful. It's like, come share this special day with us and give us money.
And most people include the gift receipts with the gift, so if you got a toaster that you didn't need, you can just go to the store and get money back for it.
The last few weddings I've been too have requested money in their invitations, it's becoming a popular alternative to a gift regarstry, I don't see how it is any different, because a gift regastry is still saying "come share this special day with us and give us a gift". No one where I live ever includes the receipt (I know that some other places that might be the custom, but I've never even heard of that happening) so they wouldn't have the option to return it if they don't want it.
What about the people that ask for money because they're moving houses and won't be able to take along all the big boxed gifts?
Well, I doubt they won't be able to... I'm sure you could fit those gifts in the U-Haul truck along with your furniture, or keep them at your parent's house until you're able to move them.
That seems tedious and expensive.
Again, I can't imagine that someone wouldn't be able to move all the gifts if they've already got a U-Haul to move their furniture to their new home.