ignorance could be a part of it. age could be another, but the biggest is probably laziness. a lot of people join after discovering magick is real, so they join, and look up how to turn invisible [example] when it doesn't work you give them the reason why and a list of things to read and do. most will leave because it involves a lot of reading and homework. the rules are the same way. people sign up and automatically go on the forums without reading the rules. i've met some people who don't even know this site has rules. nothing is without rules. many join Wicca because 'you can do whatever you want'. this is not true. Wicca has rules, while the Rede is up for interpretation and definition by your own morals, many new converts go 'no physical harm.' and call it a day.
sorry that answer was all over the place, theres many different reasons, and i feel its laziness because many people today don't want to read. or if they do, only in short amounts.