Placement of an IV catheter is an invasive procedure, that requires more than just the "ability to do it". It requires extensive knowledge of anatomy & physiology, as well as knowledge and training in advanced nursing skills.
Licensed veterinary technicians spend several years educating themselves in academic settings in order to not only possess the above skills, but to have a solid knowledge base which allows them to have exceptional understanding of the importance of not only correct placement, but asepsis and sterility, as well as maintenance, and long term care.