Most of the conventional IUI preparations requires a andrology lab with precise temparature and air quality (aseptic environment). And do not forget to have a trained personnel for sperm preparation. In-vitro sperm preparation methods require centrifugation followed by swim-up. 

A non-recommended centrifugal force can effect the sperm functions and increases ROS which can lead to sperm DNA fragmentation (damage). Sperm DNA fragmentation often associated with miscarriages. 

Secondly, the commercially avaoilable sperm prepartion medias contain antibitics as preservatives. When inseminated these antibiotics alter the endometrial environemnt and interfers with implantation process. 

Travail method of sperm preparation for IUI is gentle and do not contain antibiotics. Thus it has more success rates compared to conventional techniques.