As someone who has primarily models for the purpose of 3d printing, i feel i can weigh in on this.
I 100% agree that using printed models as finished pieces (or even kits) is a rather lazy and expensive approach. Profit margins are going to be very slim and depending on the product, people will be paying quite a bit for still unfinished piece(s). Maybe i haven't been strolling the junkyard too much lately, but i can only think of 1 or 2 projects offering prints through shapeways for people to order,s o i'm not seeing this as a huge problem just maybe not the most efficient method to get the best bang for your buck as a consumer.
As far as people complaining about offering castings and work with print lines still in it, i dont think is an issue strictly tied to printed objects. I can't tell you how many clay sculpts, pepakura/bondo pieces, foam builds etc that still have a far from finished look that needed hours of sanding or other finish work. On each one of my 3d rings i sell, i spend upwards of 5 to 6 hours per ring making them as perfect as possible so that there is no need for further work to be done by the end user. At this point, its all about the person who's making the object. If they are good and make superb quality work it will show in the finished product, so just be wary of who you buy from and know what you're getting. I know that this forum caters from beginners all the way to professionals and the various skill levels will be apparent. I do think if a piece is going to offered for sale, it should be pristine though. Sanding marks gone. Printing lines gone. Machine marks gone. Thats how i see it at least.
Concering 3d modeling, is personally my favorite form of artistic expression. Whether you're an old fashioned hands on type of person or not, i think as makers/artists and prop enthusiasts we should all respect the different forms and methods out there. Some ways work better for others. I've used many different medias out there from pencil, pen, colored pencil, paint, clay, photoshop, 3d modeling etc. Modeling is what i'm best at, but i don't think it makes me any less of an artist or less skilled than someone who does something a different way. I also am not suggesting it makes me superior to any other methodologies. 3d is the most challenging media i've worked with but its what i find the most rewarding.
As with all artists, there will be some with greater skills than others though. Suggesting that "save and print" and that any joe schmoe can do that is disrespectful. Sure anyone CAN do it, but doing it well is a whole different ball game. Anyone can sculpt or paint too, but that doesn't make them a Michelangelo or Monet.