The guns acquisition numbers are stupidly out of date and flawed from the beginning. The internet has changed commerce in a huge way.
In 2004 around 40% of the country was on line. That number is estimated today well over 80%.
In 2004 the percentage of sporting good purchased on line was around 8%. Today it is 22%, nearly triple.
To even imagine that gun sales legal and illegal, are not following the same pattern requires an astonishing level of deliberate ignorance.
Personally I know very few people who buy any guns at gun sales anymore at all unless there is a panic going on. On this very site every few weeks someone posts a thread about how much gun shows suck due to the high prices, lack of gun vendors, sham-wow promoters and various other things. Very rarely does anyone post a positive review about a gun show at all or mention a purchase.
Criminals with warrants and known felons would have to exceptionally stupid to go to one as they are crawling with all kinds of cops. Often there are a couple at the door and then a few wandering the aisles depending upon the show. That does not even count those in plain clothes. So I would say it is unlikely they would go themselves. However, "send a friend" then "buy from said friend" and "presto-chango" now instead of "obtaining the gun at a gun show" they "bought it from a friend". Although I have my doubts they would even bother with a gun show when guns are so readily available on line.