I used Siam Legal in Bangkok for me and my wife and 2 kids - they are super helpful and responsive, and it was a successful application for all 4 of us. They charge USD 295 for the initial/main applicant, and then USD 195 for any dependants added on later, plus you still need to pay the DTV fee, which varies per country.
Anonymous participant 762 People do this to ensure applications are submitted correctly, for peace of mind, there’s many rejections for people who don’t submit the correct documents.
Also a lot of people are very busy and don’t have time to do these things themselves.