Typical Mathematica notebooks (I won't say "programs") use a fair bit less than one hundred of the common functions, plus a handful of domain-specific functions from that the greater set of five thousand. At any time, you can enter ?FunctionName to access documentation far more comprehensive than most languages offer.
The UpperCaseForStandardLibrary and lowerCaseForYourCode convention actually makes a lot of sense in the context of Mathematica's primary use cases vs traditional software engineering projects. When I'm just trying to solve some problem in Mathematica, using my computer as a bicycle for the mind, I appreciate not having to putz with import statements or avoid name collisions.