Surround over Plaster walls?

I have a 100+ old house and has an old freestanding cast iron tub that has to go, I would like to replace it with an acrylic tub and surround but was wondering if it would be ok to install it over the exhisting plaster walls as i am not relishing the idea of taking down plaster and lathe. It says to install directly over studs, but most of the surrounds i saw say that, so what do you think? Is there a reason for installing to studs? If i do, is there anything i should do to the walls first before i install?

Thanks for any help!

IF you do NOT install it against the studs, etc., you will end up with an installation that looks like a homeowner did it.

If the surround is labeled "direct to studs" then if you apply it over teh plaster, it will be about 2 to 3 " to big, and over lapt the tub too far. There are other surrounds which glue up to the wall material. You will have to open the wall for the tub. They are 60" unless you get a "special", and therefore go stud-to-stud

Many of the plastic surrounds have a lip on them that is designed to be hidden by the edge of the wall butting up to the bumpout of the surround and sit on that lip, helping to lock the thing tight to the walls.