why most of the jobs are part time.?

There are many job posting each day, even though we can find some good full time jobs here most of these online jobs are part time. And they should be completed as fast as possible. Why this is happening.

because most of these jobs are posted by small business owners who can’t afford in house employees, consider a bloger who want to make some changes to his blog and he is hiring a worker. But when the work is done what about the employee
so, online jobs are posted by these type of people who want to get their jobs done by qualified professionals and the easiest way is posting a job and allow people to bid on these jobs

this is why most of online jobs are part time