Like, you aren’t necessarily next door neighbors. You’d have to take the streetcar or bus or commuter rail some distance to go meet your friend. You can’t text “sorry the train is 30 minutes late”, because no cell phones, no internet, no tracking buses or trains on your smartphone. No payphones or landlines.
Letters are only for those cross-continental, cross-oceanic relationships. If you live in the same city, then well you’d still have to meet in person cuz it’s not the digital age, no doomscrolling social media and sending texts and memes.
I feel like those were the days where you could have true friendships in society, not “having friends to send memes”.
Go out earlier is a practice that I think it is not done anymore. If I have a meeting at 4pm and I know that it takes me 30 minutes to get there, I go out of my house one hour before. This is for answer your doubt about how would you let know to your friend that you will be late, you weren’t able, the best you can do is be preventative.
Imagine you send a letter to a fellow who lives overseas, you expect to see him september the 3rd in a concrete place. I can bet that person would arrive like a month before and wait the right time. (Obviuosly would not wait for you in that very place, that person can stay in a hotel or whatever).