Free internet access applies only to dial up connections. And while the service is free, there are usually restrictions in place. These include but are not limited to: limited number of hours of use (usually less than 10 hours per month), time of day usage restrictions, access to web mail only (can't interface with popular email platforms) and so forth. Likewise, there tends to be a limited number of available free accounts and canceling your account requires a call to technical support, which involves a fee.
Perhaps the biggest complaint users have of free internet access is the number and size of onscreen ads. It is the placement and revenues of these ads that allows the internet provider to offer the free service. However the ads take up much of the available screen space and most require the user to click on them to continually to maintain their internet session. However for all the disadvantages, free is still free. For users that either can't afford it or don't have access to the internet, that one big advantage usually outweighs the restrictions. Being able to access the web (however restrictive) is better than nothing at all.