"So why not just move Visual Studio to be a 64-bit application? While we’ve seriously considered this porting effort, at this time we don’t believe the returns merit the investment and resultant complexity. We’d still need to ship a 32-bit version of the product for various use cases, so adding a 64-bit version of the product would double the size of our test matrix. In addition, there is an ecosystem of thousands of extensions for Visual Studio (https://visualstudiogallery.msdn.microsoft.com) which would need to also port to 64-bit. Lastly, moving to 64-bit isn’t a panacea – as others have noted (https://blogs.msdn.microsoft.com/ricom/2016/01/11/a-little-6...), unless the work doesn’t fit into a 32-bit address space, moving to 64-bit can actually degrade performance."
Also, a lot of people don't realize that there is a 64-bit version of the toolsets[2] (for C++ at least). I don't tend to have high memory use by Visual Studio itself but often run out of heap space using the compiler and linker so having access to those can be very helpful.
1. https://visualstudio.uservoice.com/forums/121579-visual-stud... 2. https://docs.microsoft.com/en-us/cpp/build/how-to-enable-a-6...