I also do, if only because that’s what employers ask for. However, I’m not very comfortable about an international teaching association taking such a clear position on which TEFL course to take. From their FAQ:

“Do you accredit any courses? What course should I take?

Although IATEFL does not endorse any courses, we recommend if you are starting out, to take a CELTA or TESOL course run by either Trinity or UCLES.  These are internationally recognised and will enable you to teach anywhere in the world. Before you choose your course, check with several schools or institutions in the country in which you wish to work. Ask what qualifications employers require.  Check that your chosen TEFL course leads to a recognised qualification.”

Sounds a lot like endorsing just two courses to me! Surely it could just be:

“Before you choose your course, check with several schools or institutions in the country in which you wish to work. Ask what qualifications employers require.  Check that your chosen TEFL course leads to a recognised qualification.”

with maybe some mention of the usual 120 hours with 6 hours of observed and graded teaching practice.