Is keigo/formal only used at the end of sentences?


So I was going over から, and I noticed how all the sentences had like 病気だから, or
りんごがない in the middle of the sentences, and then they had keigo/formal at the
end with ます and です. So that got me thinking, is keigo/formal just never used
in the middle of setences, and it's always the "short" version that is used?

For example:

> 今日は病気だから、運動しません。




Your use of the word “keigo” is a bit misleading. When people hear it, they
usually don’t think of です and ます although they are technically part of
“keigo”. I will call them polite forms as opposed to plain forms, which you
called “short” versions.

Some conjunctives do require a plain form but から is not one of them. You can
use a polite form before it.

> 今日は病気ですから、運動しません。

