It can.
If you have a pension, chances are the funds are invested in the market.
If you have a 401(k), IRA or a 529 plan for your children, you are in the market.
There is no reason why the average American cannot benefit from the market.
The reason why higher wages (and some other figures to be honest) can slow the market is fears of inflation.
Bonds are considered to be less risky than stocks. When bond prices drop, their effective yields rise, making them more desirable relative to stocks.
The concern with high wages is for inflation. The Fed has been pumping money into the economy through several rounds of quantitative easing. I believe the Atlanta Fed forecast some high expected growth numbers. All of this has people concerned about inflation. Combine that with the markets seeming to just keep going up, and there are some who are looking to take some profits should there be a permanent drop.
For me, with retirement some 10-15 years in the future, I simply look at this like a sale at Macy's. I took some of my raise and some of the money I'm saving in 2018 due to the tax cuts and putting it in my 401(k)
So for me, this is a good time for the markets to cool off and drop in price a bit. My increased contributions will get me more shares in the funds I'm buying.
So even market downturns can work for the average American if they keep their cool, don't panic and buy responsibly.