Not that know of any such services but even if they exist, I would avoid them. You need to be in control of your bitcoins, if you think you are addicted to gambling or something you should rather talk to your friends then giving access to your funds to any such third party services. Probably use a cold wallet and keep the key safe with your closed one.
This thread is not discussing the WHY but the HOW - why can't you keep your opinions to yourself? This is not a WHY thread but a HOW thread? (not why lock your coins but HOW to lock them).
Please save your opinions to yourself if you cannot contribute to the purpose of the thread.
Locking the bitcoins means that you are not allowed to withdraw for a certain time. If you really want this and still want full control over your coins, I will suggest to move those coins to a new wallet and keep the secret key in some lock and throw the key away. When you need those coins, you need to break that lock in order to get the secret key. I know this may seems ridiculous to you but that's the best way rather than trusting any 3rd party website.