A high score gives the company bragging rights; if the score is poor, the lab lets it know what went wrong.
When the antivirus doesn't bring in any income, a company might be tempted to avoid the expense of testing. I follow five independent testing labs that regularly release reports on their results; all five of them include AVG.
Both AVG and Avast have huge followings, but globally each is strong in different areas. Of course, AVG only makes money if somebody purchases the for-pay security suite.
There's a certain amount of upsell when you go to install the free antivirus, but it's much more laid back than, for example, Comodo.
That becomes a full circle only if you upgrade to the paid edition.