Last year the vet made a bit of a hash of one sample, this year, different vet, she took it so quick I was still waiting for it to fill and she'd done! The goats were very good, I hold them close to me with their heads up and turned towards me, makes the sample easier.
certainly with CAE testing and similar, I can imagine some unscrupulous breeders (yes, I'm sure there are some) could take from one they know is clear, instead of from one positive but worth showing or breeding from. Better to have an official stamp.
If you can take the goat to the vet it's much cheaper (however I did note the diffence of the cost on the certificate and the cost on the vets invoice, I thought naughty of the vet to add some to that as well as their 'consultation and blood sample' fee)