Normally I don’t link to pages from Google, but the analytics of Google Fonts are quite impressive. In total, over 36 trillion fonts have been loaded from Google Fonts.
However, the system fonts are often perfectly adequate and do not look bad. Also on this blog only system fonts are used, which means that there is no need to download a font file first. This saves bandwidth, reduces the amount of data sent to Google (none is sent at all) and speeds up loading. It probably even helps to reduce CO2 emissions.