Because wages are a small part of the total compensation package - leaving out bonuses, health, dental, vision insurance policies, 401k (with matching), employee stock purchase plans, stock options or stock units awards, access to food and on-site services, company cars, etc.

They’re also not stagnant https://tradingeconomics.com/united-states/wage-growth

If my employer's group health insurance is considered part of my compensation, should I not be glad that health care costs are rising, since that drives up my total compensation?

From Australia's Reserve Bank:

https://www.rba.gov.au/publications/rdp/2018/pdf/rdp2018-10....

ahem Income inequality suggests otherwise.

Income is far more equal than it was when people began worrying about automation causing unemployment (~100 years ago).