The term "commercial use" is very vague and there is no widespread agreement on what it means. The definitions range from "use by a company" to "making money by selling copies" and just about anything in between.
One of the corner stones of open source licensing (which most licenses with a share-alike or copyleft nature fall under) is that the license can not exclude groups of people and that includes the group of people that tries to make money off your product.
In this way, share-alike doesn't mean you have to share your work in exactly the same way, including the price asked for it, but it means that you must give the recipients of your work the same rights for modification and re-distribution that you received.
Because you must give the recipients of your work the right to distribute it further (with or without modification), a share-alike license doesn't work well with a business model of selling copies of your work (every customer could become a competitor who can charge less than you do for the same product). But other business models, like selling support contracts, are entirely possible with a product that has a share-alike or copyleft license.