When we say Oracle Version 126.96.36.199, it means that we have software for the base release 8.1.7 and the patch 188.8.131.52(another piece of software) has to be applied to make it 184.108.40.206. A Patch is released to overcome few bugs to the existing base release which cannot wait to be applied till the next release.
when oracle release a new patchset for your version , say, now you have oracle 220.127.116.11 installed on your production, and now the latest patchset has been released.
So, what is the rule that you apply this patchset? If the production is good with current patchset(eg, 18.104.22.168), will you choose to upgrade to 22.214.171.124?
We upgrade the software only when it is required or on a safer front that we dont hit the bugs, we upgrade it. Say ur production is running fine with 126.96.36.199, there might be possibility that the bugs which occured in 188.8.131.52 hits u someday and then anyway u have to upgrade it