It's as simple as this. Relatively few companies offered their services as cavalry until the second half of 1862. Those which did serve were scattered.

Aside from ten companies which joined the 1st Alabama Cavalry, other mounted companies recruited in Alabama in 1861 included five in Forrest's regiment, two in the Jeff Davis Legion, five in Wirt Adams' Regiment, two in the 4th Miss. Battalion and two in Brewer's Battalion as well as independent companies such as the five which later joined the 3rd Alabama Regiment, and three which later belonged to the 11th Alabama Battalion. The "Mobile Dragoons" and "Mobile City Troop" were on duty in the Mobile area, as well as Houston's and Hubbard's companies which later belonged to Roddey's 4th Alabama Cavalry. Sounds like about thirty-eight mounted companies, but I may have overlooked a few.