Some pools are willing to manually cash you out if requested, but a cash out button would allow others to cash you out anytime they felt like it since your stats page isn't private. The only way it would be feasible is if the pool made you register and you had to log into your account to see your stats, then a cash out button wouldn't be a problem, however most people don't want to register like that. Mining in a pool is basically completely anonymous.
there are anonymous pools where you can change the payout limit and confirm with the IP address of your miner - so nobody could manipulate that without knowing your IP but you have the control how often you get payouts.
if you make detailed notes about your mining with every single payout it's a nightmare to mine some currency where you get payout every few minutes - then you have few hundred payouts a day and that can't be very good for the server too if he is just busy with maybe thousands of payouts in short time. wherever possible i set the payout limit to what i can mine within 12h - so getting 2 payouts a day.
