They are like any collectable and I love them personally and know lots of people who do also
Not sure why you had to start a thread like this.
To be honest you could ask that about anything that anyone here likes. For example, why do we rebuy films we often own or can be bought for a fraction of the price of steelbooks just to own them in metal tins? Because we like them and want to collect them. Also why people spend a lot of money on hot toys or any other collectables but no one does question any of it as its kinda rude, particularly you describing pops as "...chunks of plastic.." pretty rude