I don't think it's an insecurity. The majority of juicers wouldn't even be in a gym, if they weren't on. Making decent gains without drugs isn't that easy, so many deviate to drugs.
Not that many have good genetics for lifting, so roids are a consolation prize for those and some who can't put in the effort.
This doesn't encompass all juicers of course, but the majority for sure.
If I had a dollar for every guy I saw lifting for a bit, looking like nothing, then hitting a bunch of juice. How many people are dedicated enough to eat 6x a day, train hard, etc? It's a very small number.
In short, juice is usually a consolation prize for those who looked up to Arnold as a kid and wanted to be muscular...then came to the conclusion they couldn't achieve much on their own. Luckily, juice is readily available today and helps many feel as if they accomplished something in a gym. You can't blame people for taking that route. After all, gaining 40lbs+ of muscle isn't for everyone.