Anything is 'collectable', musical instruments included. I don't begrudge anyone finding pleasure in owning any object and being fascinated by the details of it's construction and historical context. The phenomena of guitars being highly prized is a natural result of people loving the music they can create. So - folks who find such things interesting - hey, let them have their fun - it's neat stuff.
I do however strongly agree with you regarding the effect it may have on progress in creating new and possibly better-designed instruments. Recent innovations in ceramics, carbon fiber compounds, polymers, metalic alloys have yielded woundrous possibilities for creating instruments using these new materials.
However, the primary focus of most manufacturers is to churn out 'new antiques'. The Model T was a great car in it's day - but modern cars are constructed from better materials and have refinements that make them better cars. I trust that some creative luthiers are experimenting with radical 'concept instruments' (just like the 'concept cars') using new materials and new ideas . . . but the guitar industry seems mired in a rut of nostalgia.
"That darn Pythagorean Comma thing keeps messing me up!"http://en.wikipedia.org/wiki/Pythagorean_comma