Because nobody wants to be called or to call himself a 1/10 developer! It's goddamn demeaning!
And we're all at different points on the learning curves for different technologies, so we are all "1/10 developers" for some techs! But if you get the "1/10 developer" label for a technology that you end up working with but you've never touched before so you're running in the "learn on the job" mode, some will tend to mindlessly generalize this and you'll end up with a "1/10" label on your head, and you never want that, especially if you're also freelancing or doing independent consulting and your "fame" has financial consequences!. You just label the pro/experienced/uberproductive guys as 10x and leave the others to learn and perfect, it has the same "positive" effect that having a "like" button and not a "dislike" one (or both) has on social networking sites. (Now , having "learn on the job" guys working at 1/10 productivity is horrible for the customer, but this is how it works and how you get paid for learning instead of paying for learning by going to a top notch university and/or crawling through badly paid internships - as wise men said, "paying customers get shafted every now and then", but this is how we keep learning and keep our jobs fun :))
If you are consultant it is implied that you are at least proficient in technology/tools you are using and learning on the job in that case is quite frankly immoral. Especially if you are not uprfront with your client about your suitability for job.
And we're all at different points on the learning curves for different technologies, so we are all "1/10 developers" for some techs! But if you get the "1/10 developer" label for a technology that you end up working with but you've never touched before so you're running in the "learn on the job" mode, some will tend to mindlessly generalize this and you'll end up with a "1/10" label on your head, and you never want that, especially if you're also freelancing or doing independent consulting and your "fame" has financial consequences!. You just label the pro/experienced/uberproductive guys as 10x and leave the others to learn and perfect, it has the same "positive" effect that having a "like" button and not a "dislike" one (or both) has on social networking sites. (Now , having "learn on the job" guys working at 1/10 productivity is horrible for the customer, but this is how it works and how you get paid for learning instead of paying for learning by going to a top notch university and/or crawling through badly paid internships - as wise men said, "paying customers get shafted every now and then", but this is how we keep learning and keep our jobs fun :))