They are, but mostly by A level students who dont really know what they're talking about and just looking for a way to feel superior.
They sre well recognised though by the people who actually matter, over 95% of UK universities accept BTEC now and that is rising each year, which although it is not at 100% is still really good for a relitively new qualification compared to A levels.
Employers prefer BTECs and this is where it really matters, for both graduates and non-graduates people who hold BTEC quailifications come out as more emplyable, for graduates holding a degree and a BTEC the employment rate is around 80% whereas with A levels + a degree is is around 73-74%, and for people who didnt go to university it is 49% vs 45% in favour of BTEC and this isnt just for any type of employment it relates specifically to Skilled, Professional and Managerial jobs.
I myself chose to do a BTEC because I knew completely what I wanted to do, I got D*D*D* in my computing based BTEC amd am now in the second year of my MSci Computer Science degree and have a placement at a good company secured, who at my interview saif that they preferred the computing BTEC over the A level.
Going back to the point about universities, people believe that is is a myth that BTEC students are able to get into highly ranked or more specifically russell group universities, this is really not the case, it is just as easy fo get an offer as it is if you have A levels, you just need to make sure you meet the minimum requirements, have a good PS and perform well at interview (if required, usually not), people from my old BTEC class got offers from the following: Manchester, Southampton, Kings College London, Royal Holloway, Surrey, Bath and Cardiff, these were all for Bsc/Msci Computer Science or ITMB, also I knew people from the Engineering and Business BTECs who went to York, Durham, Bristol and some other top universities and are doing well, the one from York is about to finish his 3rd year in Electronic Engineering and on track for a high first class.and also last year I read (i think on the Guardian) about a student who did a Health Science BTEC (which is part of the Health & Social Care range of BTECs and is the one people usually knock for being "stupid") who got into Oxford to study Experimental Psychology and apparently on their interview didnt even mention the fact that they did a BTEC over A level, show that just shows if you can demonstrate the ability there really are no limits
NOTE: Please ignore the poor spelling its late and I'm in bed on my phone