Counter-Strike: Source (CSS) was indeed played competitively, but several factors led it to be eclipsed by the popularity of Counter-Strike 1.6 in the competitive scene. 1. **Gameplay and Physics:** One of the main reasons is due to the mechanics. The movement, gunplay, and physics in CSS were quite different compared to Counter-Strike 1.6. Players felt that CSS was more casual, lacking the skill-based mechanics and nuances that 1.6 had. Gravity, bullet spread, recoil patterns, and hitboxes - all felt very different and arguably less skill-based in CSS. 2. **Community Adoption:** When CSS was released, CS 1.6 had already established a strong, dedicated community of players and pro gamers. Many from this community felt that CSS did not improve enough on 1.6 to warrant a switch. 3. **Professional Scene & Tournaments:** The pro scene also largely stuck with 1.6. Only a handful of tournaments used CSS and thus there was a lack of incentive for players to move to CSS for competitive play. Also, many tournament organizers hesitated to switch to CSS from a well established and still growing CS 1.6 competitive scene. 4. **Timing and Transition to CS:GO:** By the time CSS took control over many of 1.6's limitations and became more refined, Counter-Strike: Global Offensive (CS:GO) was announced. Most of the competitive player base transitioned directly from 1.6 to GO, skipping Source. In a nutshell, while Counter-Strike Source did have a competitive scene, it was far less dominant than that of 1.6. The competitive community felt 1.6 offered the more precise, skill-based game that is essential for esport competition. CSS, while a good game in its own right, couldn't pull the established user base from 1.6 and eventually got overshadowed by the popularity of CS:GO.