The whole story (from wiki):
7 for all Mankind is often misassociated with the denim brand Seven 7, a separate company that has been established in Europe since the 1960s. "Seven7" Brand immigrated to L.A. and continues to manufacture a slightly lower-priced denim with a similar fit in both the US and Europe. Seven 7 was reintroduced in the United States around the same time as 7 for all Mankind, who filed a lawsuit against the company for stealing their name. The court war continued, in the European field this time. The registration of the word 'Seven' as a jeans maker belonged to the 'Seven7' brand from the 60s. The court decided in Belgium that "7 For All Mankind” ceases to use the sign 7 or “Seven” even in combination with " For All Mankind”. "Seven7" licensee in Europe drove the Brand in big success the past few years, lifting the quality standards to extra premium denim, introducing the embellished category in denim, decorated with Swarovski crystal. Other denim brands, including "7 For All Mankind” followed this trend. Price points where also driven to extra premium denim standards, establishing the "Seven7" jeans among the most desirable fashion items. The European Licensee regenerated the “Seven7” essence of the 60s, combining the original “Seven” design values with L.A. style. "7 For All Mankind" and "Seven7" represent style and status.
The name "7 For All Mankind" is inspired by the statistic that most Americans own an average of seven pairs of jeans at a time.