While the availability of drivers in the Linux community is indeed rather uniform, several factors contribute to make this general picture less than perfect.
The uniformity in driver availability you are referring to certainly applies to those which enter the kernel tree. Once this is decided, support for the development of drivers under evolving kernel structure lies squarely with the Linux kernel group, and you may rest assured of the availability of said drivers from some initial kernel version onward.
However, there is also a large group of proprietary drivers which may not, for obvious reasons, find their way into the kernel tree. Or there are drivers which require proprietary firmware, which are not necessarily installed automatically, depending upon how strictly the distro developers adhere to the principles of FOSS (Free Open Source Software). For both of these types of drivers the degree of support (to say nothing of their technical adequacy) by their rightful owners is not constant with time, as in the case of the Broadcom wifi drivers; hence the need for the development of FOSS alternatives. A famous case, apart from the Broadcom, is that of the OpenSource NVidia drivers. When an open source alternative does not exist, you may find that some drives are compatible with older kernel versions, but not with newer ones; in some cases compilation with up-to-date Linux headers is not an option, simply because they may refer to system calls which do not exist any more.
Also, new hardware is normally introduced between different kernel versions, which may be (trivially or not) accommodated by existing drivers. This is the case for instance of many wifi adapters, which producers present as brand new as some point in time, but which are instead based on pre-existing chipsets for which a Linux driver already exists. In some cases, a trivial code modification plus re-compilation solves the problem permanently. Other times, more complex modifications to the driver are needed, or even the introduction of an altogether new driver. Luckily for us, in this case the generous folks at Linux Backports provide us with versions of new or modified drivers which are compatible with older kernels. So, even if you feel left behind, downloading backports from this site will allow you to sport the newest drivers around.
In other words, a little bit of work is needed (download and compilation of the Linux backports) to restore the near uniformity you were referring to.