Your friends tells you about this thing which he believes in and tries to convince you. But you're not sure.
a) Go along with them, get absorbed, spend hours listening to their arguments, ask around a circle of friends that you share with him about their opinion? (i.e. imagine pre-Internet generations where if you didn't know someone personally, or were a part of a group, you didn't even get to meet them, let alone communicate extensively)
b) Go to your social network online, look up vast resources, have the arguments for and against in front of you, find out all the dirty secrets, cliques, etc. hear tell from friends-of-friends-of-friends about things they do and believe in?
It's just a product of information availability. And it works both for and against us now. It's now harder to quash rumours started by a random person with no basis from spreading but it's much easier for such rumours to reach the ears of the interested - even if subject to court order in some cases!
And it's not just religion. It's products, services, celebrities, charities, you name it. Before, you didn't have a source of information likely to know both sides and the in and outs of everything that you could consult confidentially and extensively and get THOUSANDS of peoples opinions in a matter of minutes. Now it's a click away and you're taught to use it for school research before you're able to write.
On a personal note, I'm agnostic, so it's no great surprise to me that the more facts people have available to consult, the less seriously religion is taken. "Faith" is something I see as laziness - "I don't want to check this fact, I'll just trust it's true" isn't the best principle to live by. In fact, it's that exact principle that is being eroded by the simplicity of fact-checking nowadays (even if not perfect, there are still good sources of actual fact rather than common belief out there).
Religion has been on a bit of a death-spiral for years. My country is pretty much turning churches into nothing more than pretty historical buildings that you visit and feel obliged to drop a coin in the box to pay for your nice photos of the stained-glass. My father-in-law is religious and bemoans the complete lack of religion in his local area - he visited dozens of churches before he found one with any kind of active services, and they didn't suit his preference.
By contrast, he says that the US is a much more faithful country and you can still draw crowds of tens of thousands at certain churches.
But I think that's more about celebrity, and the older generation, than anything to do with religion itself.
Religion is dying a little, but to be honest we were in a kind of renaissance of religion the last couple of hundred years anyway.