[SkyPuncher]

A reddit comment had a pretty good explanation.

Most malicious code is still written in 32-bit since 64-bit Windows supports running 32-bit code.

Write something in 32-bit - target 100% of devices. Write something in 64-bit - target ~50% of devices.

[Zuider]

But if security software only treats 32-bit executables as suspicious, wouldn't it make sense for malware creators to switch to 64-bit?

[firethief]

Is any security software that easily bypassed?