Haiku is full of little interesting design decisions like this. I would _love_ to have it running on a laptop (nearly there) or a Raspberry Pi (sadly, not likely to happen soon, because the initial ARM developments sort of shunned it and it's taken them a good while to re-focus).
Haiku's goal is being a full-fledged desktop/laptop OS, not a "mobile" OS; and most laptops and desktops right now are all x86, so that's what we primarily target.
What's preventing you from running it on a laptop now?