1 simple Fact there is nothing unlimited.
There are some limitation for everything, can you tell me anything which is having unlimited in it, the answer can be it's in abundance but not unlimited.
An average site do not go over 10 GB (At least, I Think So).
Yes unlimited mean no set limits.
If a service provider run out of space / any other resource they pay and buy additional resources.
Also it we try to see the reseller service provided by the unlimited web hosting provider they have a fixed resource uses limit(At least 90+ % hosting providers)and not ulimited.
SORRY MY ANY FAULT OF MINE.