Personal Philosophy
There are many things that make small cap stocks unique, and that is why a lot of institutions and certain investors tend to not have much exposure to them.
These are some of the reasons
There is less information about the companies in general, media coverage can be very limited at time
A lot of times they are known or well known in their region and not always nationwide. Think about local fast food chains vs. the franchises like McDonalds or Burger King
Some investors limit themselves market cap
Often times, the companies themsleves are at a more beginning stage, and many investors don't have the time or the stomach to see them to fruition.
The industries themselves tend to be young, you do not start in a unique industry or with a unique business model with an exorbinant valuation, 9 times out of 10.
On the other side of this there just as many reasons why you should be looking at small cap stocks.
The finders fee: many institutions and large investors want a good number of analysts covering the stock. So many times, companies only hit their radar given a certain statistic such as: 5 analysts, revenue of $3 Billion, or Market Cap of at least $2 Billion. They simply do not want to waste their time in most cases researching potential stocks that do not their specific requisite(s).
Media coverage from financial outlets like Bloomberg, CNBC cover the big dogs like Apple, Google, Tesla to name a few. The viewers want coverage on these stocks because they are the ones that influence the market and are most popularly owned.
If you are looking for companies that have great valuations that would be "safer investments" from that standpoint, you would find a lot more of these companies under $1 Billion rather than companies that are higher than $40 Billion. Simply because there are only about 400-500 companies that have $40 Billion+ in market cap.
The diversity in business models is much more vast with small cap stocks. This is a double edged sword, while some are on the edge of innovation others are on their last legs.