Gabriele,
Right, not sure if you want to know what a scrub gets used for, or why people are buying them all, so I'll attempt to cover both.
First of all a scrub is really only needed if you're converting rough sawn wood entirely by hand - I don't do that, so this is all theoretical. Whether you need a scrub or not really depends on the state of the wood you are using, in my opinion. If it's fairly square and straight and more or less the thickness you want, you can probably do just as well with a jack plane and save yourself the effort of planing out the marks of the scrub. However, if you need to remove a lot of wood, either to get down to a cetain thickness that you can't saw to for some reason, or to remove some serious cup or twist in the board, then the scrub comes in as a quick, but rough, wood remover. I tend to think of it as coming somewhere between an
adze and a jack plane, although an adze is arguably capable of finer work in skilled hands than a scrub... (I now await correction from more knowledgable scrubbers)
Why are they all being snapped up? My guess is the Lie-Nielsen effect. I've noticed that often when L-N have come out with their version of a model, all the old versions suddenly get very popular. It certainly happened with the Record #073 shoulder plane quite noticeably. Presumably people thing "well, if they think it's good enough to be worth making new versions of, then it's worth buying the old ones". So they do. Also, largely because of L-N, scrub planes have had a lot more coverage in recent times than they used to, so increasing the market. My theory anyway.
Have you thought about making your own scrub plane? It's just about the easiest plane to make because you don't have to worry about the size of the mouth.
Cheers, Alf
