Should I use the default locale in the url, or not?

Question

Search Engine Optimization

What pitfalls can appear in the future if you hide the standard locale in the URL?

// Вместо
site.com/ru/about
site.com/en/about
site.com/fr/about 
// Вот так
site.com/about
site.com/en/about
site.com/fr/about

Answer 1

There are no problems. It has no effect on indexing. And users do not look at the number of letters. If only the language switcher worked adequately, substituting not the main page, but the current section in another language, if there is a language copy

Answer 2

The link may be broken if the pages have already been indexed. Don't forget to set up a regular redirect