Phonetics isn't my forte but I might offer some help.
I am aware of at least two theories that try to explain why certain sounds are more wide-spread than others. The first one is called Quantal Theory, proposed by Kenneth Stevens (1972, 1989, 2002, inter alia). There are regions of stability in the articulatory to acoustics mapping (aka quantal regions), when changes in articulation have little impact on acoustics. Sounds that occupy those stable regions tend to be more common in languages. Have a look at this handout
The other one is called Adaptive Dispersion, first proposed by Liljencrants & Lindblom (1972) (the 1971 working paper version can be downloaded for free). Its basic tenet is that sounds in a language tend to be placed in such a way so that perceptual (auditory) contrast between them is at maximum. See this paper by Keith Johnson
Liljencrants J, Lindblom B. 1972. Numerical simulation of vowel quality systems: The role of perceptual contrast. Language 48, no 4, pp839-862
Stevens, K.N. 1972. The quantal nature of speech: Evidence from articulatoryacoustic data. In Denes, P.B. and David Jr., E.E. (eds.), Human Communication,
A Unified View, 51-66. New York, McGraw-Hill.
Stevens, K.N. 1989. On the quantal nature of speech. Journal of Phonetics 17, 3-46. [the same issue of JPhonet. contains multiple critical responses to Stevens' theory]
Stevens, K.N. 2002. Toward a model for lexical access based on acoustic landmarks
and distinctive features. Journal of the Acoustic Society of America 111, 1872-