There's actually still a fair number of people who get their first COVID-19 infection and never develop any symptoms at all, although it's a lot less than the initial research indicated early on in the pandemic: https://jammi.utpjournals.press/doi/10.3138/jammi-2020-0030

But a much bigger problem is presymptomatic transmission, which is why this disease was able to spread so steadily. Aside from that, there are people with symptoms that are so minor they never even consider themselves sick (although hopefully today people are more vigilant about this).