Bit by bit, the PC world is continuing to drop its legacy support.
There will be another year of security updates for 32-bit drivers, but all new features, performance enhancements, and support for new hardware will require the use of a 64-bit operating system and 64-bit drivers.
Reasons to stick with 32-bit Windows are at this point few and far between. 64-bit Windows has superior security to 32-bit, and while it varies with workload, 64-bit applications can run somewhat faster than 32-bit counterparts; for workloads that won’t fit within the constraints of 32-bit software, the difference is of course enormous. Generally, those who continue to use the 32-bit operating system tend to be subject to some kind of legacy constraint. 32-bit drivers won’t work in 64-bit Windows, so obscure but mission critical hardware can extend the life of 32-bit systems.
There can be software issues, too: 32-bit Windows can run both 16-bit Windows and 16- and 32-bit DOS applications. 64-bit Windows cannot. Virtualization software such as VMware, or emulation software such as DOSbox, is arguably the better option for anyone who still needs that kind of compatibility.
While the PC has a long history of backward compatibility and legacy support, 16- and 32-bit software and ancient hardware are set to become a lot harder to use in the next few years. The loss of driver support is one part of this; another is Intel’s plans to drop BIOS compatibility from firmware by 2020. This change will make it impossible to boot all 16-bit (and almost all 32-bit) operating systems on modern hardware.