system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there a Windows 32-bit and 64-bit?

It seems to be a headache for developers. Kerbal space program for instance, a regular 32-bit version and a 64-bit version that is buggy and has to be maintained, meanwhile being highly requested by a community who have 30+ mods and no RAM to spare. 

64-bit seems better in all respects. It is also a higher number. Why wasn't Win 32-bit phased out ages ago and everything would be 64-bit and fast like a racecar?
gpt
Because Win-32 was a standard for many many years and a lot of people aren't interested in buying a new computer that's required to move beyond it. 

The 32 bit register was an absolute rock-solid performer as a desktop CPU throughout the 80's and 90's. It provided more than enough power for the applications of the day, and if you wanted something more powerful (something that really only hobbyists or businesses needed or wanted), you simply bought a beefier non-desktop computer. 

Then, as we continued to ramp up the complexity and amount of information that our computers had to handle, and as they spread everywhere, it was necessary to increase the amount of variations of instructions and information handling that the computers could perform. They did that by adding more bits to the registry, moving the industry to 64-bits. And because the way the computer worked to be able to handle these extra bits was so different, you needed a new 64-bit operating system.

But going to 64 bits also required you to buy an entirely new computer... and that was something that a huge part of the market wasn't interested in doing. They were happy with their unit's 32-bit performance, it suited them just fine because they weren't power users wanting the latest and greatest capabilities.

So the market had to split into the part that services all of the older 32-bit systems out there, and those that wanted more performance on a 64-bit machine. Since there's no one monopoly supplier that could tell the whole market "Upgrade now or I'll turn off your computer" without driving themselves out of business, movement to 64 bit is a gradual thing as people replace their older computers, and 32-bit systems still need their own software versions.