I teach btec and gcse sciences, the current btec is worth 2 gcse passes at c-a deepening on the btec level achieved.
Btec is used to students who would NOT achieve a grade C at gcse, in some cases, they have sat the core science gcse in yr 10 and struggled so moved on to btec.
The kids who are very weak academically respond much better to this kind of continuous assessment, and on the whole tend to go in to vocational training after school where the ability to study in a btec-like manner is an advantage to them.
In terms of the science btec, it was never designed for academic kids, however the a level equivalent is accepted at uni for certain science courses as being academically rigorous enough to prepare students.
Being able to offer our weaker kids btec means that they are engaged, they can see that they are going to achieve something, they are going to get something out of this course, and as a result,they put in a lot of effort to achieve well, most not just settling for a pass. If they were studying gcse, the vast majority of these kids would really have struggled - not to mention the behaviour issues hat would result - how would you feel if someone told you that your target grade was an E, highly unlikely you would bother to do any work I guess, at least with btec, they get something valuable.
I think what Gove forgets is that not all kids are academic, and not all careers require academic qualifications, vocational routes are just as valuable!