More load does not just mean needing to increase capacity, which would be simple for Microsoft to do.

Additional load reveals limits and breaklines that were never known before - your temporary integer IDs are suddenly too small, you reach the maximum file descriptors in a Linux distro, your hash function suddenly has repeating conflicts, your DB index is suddenly oversaturated.

Having massive exponential growth of your traffic would probably require constant refactoring to meet the ever changing system limits.