Individual rank-and-file employees don't get promoted for not building features. So there's an inherent incentive for the app size to grow, whether or not that

Individual rank-and-file employees don't get promoted for not building features. So there's an inherent incentive for the app size to grow, whether or not that code is useful to 99% of its install base. Between writing a single line that includes a 100 MB library and writing a hundred lines that include just the code needed; many people will pick the former. Just look at usage of GPUImage or other libraries.