VLB was a stopgap solution to fix ISA. The 16-bit ISA bus originated in the original PC AT (1984) and was showing its age by the time of the 486. Not only was it 16-bits, system designers had long since decoupled the slot clock from the CPU clock to maintain compatibility with cards that assumed 8MHz.
The issues with this bus were evident as far back as the mid-1980's. IBM's evolution of ISA was the Microchannel (MCA) bus. It was a better bus than ISA, but it also had it's problems. MCA boards were about half the size of ISA boards, required more complicated glue logic, and there were licensing fees to be paid to IBM if you wanted to build an MCA machine. Tandy did this with the 5000MC, but very few others did. (Other issues with the MCA bus included the fact that there were performance issues in the PS/2 Model 80's implementation of 32-bit, and IBM itself undermined the bus by continuing to use ISA in the Model 25, 30, and 30/286.)
The troubles with MCA and the limitations of ISA left a vacuum that an industry consortium attempted to address with EISA. EISA had backward compatibility with ISA (including card size) and many of the same features of MCA, but was expensive and mostly wound up in servers and other relatively high end machines.
The net effect of all of this was that, particularly in the low to mid range market, PC's wound up confined to the 16-bit/8MHz ISA bus well into the 486-cycle. For most peripherals, this didn't matter, but fitting a 1024x768x8bpp display through an ISA bus represented a major performance bottleneck. This became even worse at 16bpp or when trying to animate things. (This is why NeXTStep required a better bus than ISA, and on-card video accelerator chips didn't help.)
And this is the gap that VLB was intended to fill - how to get large bitmaps into a frame buffer. Very little else was in scope. As a result VLB was designed in much the same way as ISA was originally, with the same bus and clock rate as the host CPU. With a 33MHz FSB, the VLB would run at 33MHz. With a 50MHz FSB, it'd run at 50MHz. This also had an impact on the number of slots... by the time you got to a 50MHz bus, I believe only one VLB slot was allowed. This turned out not to matter, because 486DX50 machines were difficult to engineer and the market quickly shifted over to 486DX2/66 machines with higher core clocks and 33MHz buses.
The net result of this is that the market for VLB cards was heavily biased toward video cards. (Which aligns with the fact that the V in VLB stands for VESA.) That said, there were also disk controllers and a few other types of boards, but they were never remotely as significant as video. If you really care about high performance disk or network I/O, you'd buy a machine with an EISA bus. (And there were EISA machines that had VLB slots as well for the video... VLB had higher raw transfer rates than EISA, so it was still useful for video even on EISA machine.)
With the Pentium-era, Intel immediately pushed PCI into the market as the high-end alternative. Pentium-class machines would have PCI for disk, video, and anything else that required performance, and have an on board bridge to some ISA slots for compatibility with legacy devices. While I believe there were some PCI motherboards with VLB/ISA slots, the market really shifted over to PCI. (Until AGP was introduced to solve the same sorts of video bandwidth problems for PCI machines that VLB solved for ISA machines.)