While I do not know this to be a fact, it would not surprise me if Epic used 32 bit to keep compatibility with some of the older games in its inventory. As mentioned above, I do not see a problem with the launcher being 32 bit.
Have you checked with Epic or looked to see if there is a 64 bit version?
I checked with Google and the very first result that I looked at comes from Epic themselves.
"Why did the Epic Games launcher install in a 32-bit directory when my computer has a 64-bit operating system?
There have been recent changes to the way the launcher is downloaded and installed on Windows in order to have 32-bit compatibility. The initial msi installs a 32-bit program that then detects whether your system is 64-bit or 32-bit and installs the correct version of the launcher. Because there is already an existing Epic Games folder created by the program in the 32-bit directory, the launcher installs there regardless of which version it is. Your system should have the 64-bit launcher installed, it is just installed in the 32-bit directory. This is a known issue."