I play the lottery online in the UK. I buy for 8 weeks at a time - Weds. and Saturday and play the same numbers.
It's not a waste of money to buy tickets here as the profits go to good causes which I can see for myself. Places can apply for lottery grants to help fund projects - art, history, music, sport, environment. Just in my area there is a sign at my leisure centre (gym) that says it was partially funded by Lottery Sports, the 400 year old church down the road is being refurbished by a grant from Lottery Heritage, some of the British movies I've watched have been partially funded by Lottery Arts, in the summer the fiddle workshops are funded by Lottery Arts.
So, no, not a waste of my money. Yes, I would like to win as well. I occasionally buy a Euromillions tickets as well. Someone across the loch from us won £160 million in Euromillions a few years ago.
Oh, and over here you get the full amount. Tax is not taken out.