#wool tops

You know those multicoloured batts you can buy?

Do they have a purpose, beyond looking pretty and providing a ready-made colour palette?

If I wanted a multicoloured yarn, couldn't I just buy separate portions of wool tops in the colours I wanted, then spin them together? I would probably end up with less closely blended colours than if they were dyed onto the same batt, but from what I can see people often split their batts up by colour anyway, precisely to avoid all the colours blurring together.

Is it to do with the difficulty of joining different portions of wool top together when spinning? Do they have to be combed together before you start to avoid a weak or messy join?