Many altcoins have low volumes because the team is still under development. I'm sure if the team has worked hard and the development of altcoin is successful, there will be a lot of interest in the market and the volume soars.
This is the excuse I have heard most often. During the past 2-3 years, we had at least 5,000 ICOs listed in the cryptocurrency market (a conservative estimate). And I would say that more than 95% of them are currently trading below their ICO prices. A majority of these projects are no longer listed in any of the exchanges, as they got delisted due to low trade volume. Those who invested their hard earned money in these projects lost all of their capital. Only a few dozen, or a few hundred at the most are trading at a premium.
Now here comes the question. Had the development goals been completed on time, their exchange rates would have been the same? In every single project where the price went down drastically, you can see that the development has been either completely stopped or slowed down to unfeasible levels. If the investors feel that a project may not get completed in time, then they don't have any persuasion to invest in it. And that is what causes the steep crash in the prices.