The commenter actually didn't say where they lived, and didn't limit the question to any location. I live in Kenya and my one year old walks around a lot of the time without shoes, which is a calculated risk. I assure you I'm being neither silly nor worrisome - I just factually answered the parent's question about what the potential issues are with not wearing shoes.

edit: to be less vague:

(1) Tetanus spores are present in soil all over the world and can easily infect a cut on the foot - between 1 and 2 in 10 cases are fatal (https://www.cdc.gov/tetanus/index.html).

(2) Hookwork larvae are present in soil all over the USA (and many other places) and can infect through intact skin - not fatal but can have unpleasant complications (https://www.cdc.gov/parasites/hookworm/)

(3) bilharzia infects through skin contact with contaminated water which includes puddles and just wet soil - not in the USA but many other countries - and kills tens of millions every year (https://www.cdc.gov/parasites/schistosomiasis/index.html)