I was of this same mindset when I first started testing out Haiku, so I get where you’re coming from.
While it might not seem a logical move to attract new users with old applications, that’s not really who the 32bit version is built for. It’s built to give continued functionality to BeOS software regularly used by people who enjoyed BeOS.
One does not necessarily have to have 32bit hardware to use a 32bit OS, and many users and devs themselves are certainly running the 32bit version of the OS on newer hardware for the simple sake of having access to those applications. Since nightly builds are automated for both 32bit and 64bit versions, there’s not really a labor issue keeping two separate spins going at once.
Even Canonical only dropped 32bit installer support a year ago with Ubuntu 17.10, and many of the other flavors of Ubuntu are only getting around to dropping it with their 18.10 releases this month. Still further, though, that doesn’t mean the 32bit versions of these OSes are actually gone or unsupported for the time being. Ubuntu 16.04 LTS, the last core Ubuntu LTS with a 32bit image, will be supported with new updates and fixes until 2021.
Seeing as Haiku hasn’t even hit a full and proper R1 yet, let alone a biannual release cycle with 13 years of stable releases built on a 25 year old system and running a kernel with the development scope of Linux, I don’t see a real issues with meeting the project’s initial goal before bemoaning how it’ll never take over the desktop world.
Let us not forget: even as ubiquitous, pervasive, and important to the fundamental running of the modern world as Linux may be, even it never won desktop majority. Certain Linux based OSes have done well, but Windows ships on every PC sold on multinational scales and OS/X on every Mac, and as long as it’s easy to use and affordable most users don’t care what they’re running.
For everyone else, though, there are alternatives, and Haiku aims to be an alternative. One that had a specific goal at the start and has grown from there while maintaining that goal in mind for their R1.
If you don’t need old BeOS application support, or 32bit hardware support, use the 64bit image. I do.