A heavy duty landscape fabric is best used as a temporary solution for weed control. You can lay it over sod but if you are going to cover it with soil or organic mulch, you should know that it will not stifle weeds or grass growth forever. So it's basically a temporary solution when it comes to weed control but if you can control a range of external factors then you may be able to benefit from it for several years.
This may be sufficient for a number of people who may only have a need for them for a limited time period. It is a good way to initially kill as much of the sod as possible without using harsh chemicals. The quality of landscape fabric varies from manufacturer to manufacturer and it is not just about the thickness of the fabric but its colour also can make a difference to your success rates when it comes to controlling weed.
Instead of listening to others who may not be a fan of these fabrics for landscaping and weed control, you may want to actually give them a try especially so when you only intend to make use of these fabrics to control weed for a limited time period. You should always be giving preference to a heavy duty landscape fabric as opposed to lighter ones which can easily be damaged due to extreme weather conditions.