Some have manufacturer warranties. Be sure you understand which is which. For example, most pumps and filters have warranties backed by manufacturers. In many cases, these manufacturers are national companies and will be around a long time. If the company is no longer in business, then the warranty is gone.
Some contractors do their own selling, building, and warranty service.
This often spreads their time too thin and doesn't allow enough time to do what needs to be done. For example, a 10-year filter warranty normally only pertains to the filter housing. All internal parts are not covered. Usually it is the internal parts that need replacing from time to time. Another example is pool cleaners.