So, I'm wondering... if the shakha's are still there, not all of them, but some (majority? Less, more?) why are there so many different interpretations attempting to understand vedas (other than those interpretations that try to prove the views of their selected school of thought to be consistent with the vedas despite contrary evidence)?
It's not that there are different interpretations. But, rather, there are different precedences or pramANa-s.
ShAkhA-s have their own exegesis. However, their theological route is similar to adhidaivika which is an analysis of cosmological, ritualistic, psychological factors. The keyword here being ritualistic.
Each shAkhA specializes in a certain Veda. And, there will be many shAkhA-s for one Veda. This does not mean they have different interpretation, but rather their approach to the Shruti is based on various precedences or pramANa-s. This diversity is actually a good thing, because it is in line with the Vedas, especially the Rg-Veda:
The conduction of various rituals and how they are conducted sustains Rta, placing nature around us in equilibrium due to the mystical sounds resonating with it.
Each various input (i.e., "different interpretations") helps in this.
However, allow me to offer a historical view to explain why there are many shAkhA-s and how that can be confusing.
The phrase known as "Vedic Religion" was never a monolithic entity (hence the various shAkhA-s and approaches). However, all the groups that are of the "Vedic Religion" were of the yajna-dharma. At this time, the Vedas were not written, but rather orally transmitted. Since the medium of a written scripture is now taken out of the equation, we should see various Rishi-s and their shishya-s - which should result in "differences".
...then why are we (the holi polloi) doing our own thing, interepreting everything, most likely incorrectly?
Well here's the thing, Brother En'me:
Many that "study" the Veda, not for theological-reasons but for rather socio-historical reasons, will take an Indological route in understanding them. This is only a historical approach. It is not a Hindu approach. The problem arises when one utilizes an Indological approach to help themselves with a theological perspective. This is definitely not a traditional thing to do, to mix the two. History is awesome, no doubt. But, it's a different playing field. Many, therefore, opt to do their "own thing" most likely interpreting things "incorrectly" or rather of their own accord, probably because they are either harmonizing an Indological approach with what they believe passes for theological, or they don't want to ascribe to the traditional roles of acquiring such knowledge from shAkhA-s and opt for self-study - which would borderline 'arm-chairness', whereas pure Indology and pure theology are rather "hands-on" than 'arm-chair' stuff.
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