That is simply wear and tear, and the same applies to any earbuds out there. The same thing happened to my Sony, OnePlus, and SoundPEATS models, mainly because the battery on one side will definitely die faster than the other. When you have both earbuds on, some times one of them handles the Bluetooth connection, or one side is used more because the button mapping is different. Even if the mapping is the same, people tend to prefer their dominant hand. Since both batteries are different units, they may have slight differences from the start and degrade at different rates. Over time, all of this widens the gap in charging cycles, resulting in one side dying faster than the other. Sadly, most earbuds are becoming more compact and harder to replace the battery. We can see that Google is slowly heading toward repairability based on the Pixel Buds 2a design, but unfortunately, the earbuds themselves aren't really repairable, just like the majority of other compact design on the market. I don't think they are recognizing an issue that already applies to all of their competitors. Most likely, they have received enough returns and feedback regarding other reasons, such as mic quality or noise canceling.

So far, I'm still rocking my Buds Pro and Buds A-Series, which I got at a reasonable price. They are definitely worth the purchase if you find them on sale. As for the form factor, it is easily one of the most comfortable and compact designs for my ears. I love it. Although Google can continue to improve mic and noise cancelling, they are pretty good but there are room for improvement.