according to StatCounter's data

Our tracking code is installed on more than 1.5 million sites globally.

Source: https://gs.statcounter.com/faq#methodology

Such statistics are always to be taken with a grain of salt.

There are more than 1.5 billion websites worldwide. Statcounter therefore covers only a small fraction of them. So chances are good that you as a Linux user do not use any of these 1.5 million websites that Statcounter uses to create their statistics.

Furthermore, I suspect that many Linux users use tools like uBlock Origin or Pi-Hole, so that the things that are used to track users are blocked.

Apart from that, I have several Linux installations with which I never access a website. Sometimes they have no direct connection to the Internet. Thus, they are also not recorded.

But now to the most important. 3 percent of what? Percentage numbers don't tell anything if you don't know the number of users behind them. Let's assume that there were 2.8 percent Linux users in May. In June, only 2.6 percent. Nevertheless, it is possible that there were more actual users in June if the total number of all users increased accordingly.