Not everyone who lives with their parent's in their 30's is the same...
I moved out of my parents house when I was 24/25 (2005/6), spent a year living with some friends in the same city, then moved 160 miles away (Peterborough to Bristol) with a mate, partially as he'd met a bird there and partially because jobs in the area at the time were drying up big time.
Spent a few years in Bristol living on my own or sharing with one other person (the mate moved back after 6 weeks

) and then in 2013 at the age of 32 I moved to Kent during end of the recession, again due to work - my parents had there moved from Peterborough a few years prior to that, as the job situation hadn't gotten any better, and my sister/BIL and niece were down here, and so without a job here I moved in with them.
I started a new job in April 2014 (still here and happy

) but this was in a new career so I had to start on the ladder all over again, and was in the process of looking for my own place as of the end of 2015 as I was settled and had put a bit of money away. Unfortunately, the rented place my parents were in gave them notice around Christmas so they had to find a new place to live.
The housing situation here in Kent then was pretty grim, £700-800 per month for anything decent, and anything decent at a OK price was literally going off the market in a few days....
So, it was decided that we'd get a decent, slightly bigger place between the 3 of us, and I'm currently still living here, at the grand old age of 35
Just been having a look at houses round here and it's not gotten any better, if fact it's worse than it was! £800 pm for a manky 2 bed terrace in a dodgy part of Medway....

If I was to move out now, on my current wage, and get my own place (not a house share) I would literally have pennies left every month. In my current situation I have a few hundred quid left over, which isn't a lot either but gets me by and lets me put some money away most months.
I don't run an expensive car/bike, I barely drink, smoke etc and my outgoings after rent/bills (covering insurance/petrol/mobile phone) are less than £200 a month.
Some of us do live with their parents in their 30's, not through choice, but because the only other option is living what would be barely a life at all... surviving on a few pounds a month after food/rent/council tax/normal bills isn't living.
Now, I won't be here forever - but in the meantime until my career gets off the starting blocks (fingers crossed for a 25% pay rise when I get to the next step on the ladder) I'll have enough to get a decent place in a location where I won't have to worry about the drug dealers down the road, and be able to put petrol in my bike to get to work the next day...
Times are tough for single people trying to get their own place, especially in the south east. Unless you're happy in a dodgy 1 bedroom flat or sharing with 2/3 other people you're basically
****ed if you're on a 'normal' wage - i.e. under £30k. There's people in my workplace on much more money than me (£30k+) at similar ages who are house sharing, 10 years ago you'd have a damn nice place for that much and still have money left over to waste at the weekend.