looking beyond design, a lot of them are very impractical.
why?
because logos are not meant to be viewed on high resolution computer monitors.
It's going to be printed on business cards, newspapers, vehicles, uniforms, products, brochures, boxes, company stamps (or 'chops'

not postage stamps), and may even be engraved on products.
1) Cost: it is cheaper to print monotone solids than multi colored gradient and the like. And IMO, majority the 'new' design 'textures' ( gel, plastic, metallic, translucent ... maybe with the exception of solid 3D ) are playing with gradients....multi colored gradients.
2) Visibility: un-solid design are less visible compared to solid design, and are harder to change color when applied to a media which is the same color as the logo. e.g. a solid white logo can be changed to black when you want to print on a white brochure, it is harder to 'adapt' when dealing with gradient-ish logos.
3) Limitation of media: As mentioned on point 1, the logo might even be engraved on products (e.g. computer casings). It is extremely hard to accomodate the newfangled designs in such situations especially when the logo has no main outlines.
4) Cost: Just want to state again the important of cost cutting for businesses. difference between 1 color print and 2 color print means a lot of money long term.
5) Quality: Again, you are not going to view the logo on your high-res monitors. The outcome of dithering colors or solidifying it is dependent on whether the logo you make 'degrades gracefully'.
realistically speaking, design concepts take a backseat when it comes to businesses. It is hard to find a good reason to implement gradient-ish logos over solid color logos.