If you want to keep a 1 mb file on your computer’s hard disk, you will have to have that available space on your local computer’s hard disk. However there are few advantages which were noticed eventually. example: limited storage space, hardware crash (data loss), data can only be accessed on local computer.

Now when cloud storage took place, this risk vanished and better ways to access data were discovered. Example: No hardware crash risk (cloud servers do replica backup to other servers, no data loss), unlimited storage, data can be accessed anywhere in the world even from your smart phone.
Now cloud mining is just that concept, you dont have to deploy your own miners, you dont have to configure your own networking system, no internet maintenance, no worries of downtime. Hence, great mining output.

So when you calculate, these cloud mining centers earn from subscriptions and the percentage saving on Bitcoins.
Advantage:

• No added electricity costs
• No equipment to sell when mining ceases to be profitable
• No ventilation problems with hot equipment
• Reduced chance of being let down by mining equipment suppliers.

Disadvantage:
    

• Risk of fraud
• Opaque mining operations
• Lower profits
• Lack of control and flexibility