I see things a bit different with captains (and not only because I was one many, many years ago). In most armies captains have significant leadership roles whereby they command companies. The commonwealth system gives that role to majors. In Canada we have made captain a mostly automatic rank and created the curious establishment position of Capt/Lt (Last time I looked the CAF RegF had some 250 Lt positions; 2,500 Capt/Lt posns and just over 5,000 Capt posns) Effectively our captains command primarily platoons and do low level staff work.
Personally, I see Lts and WOs command platoons and captains companies - but that's just me obviously.