As I know, the ending -시 is added to the verb stem to show a courtesy to somebody. But also I faced some cases with
1) -주 endings instead of -시 (미래도 희망도 다 맡아주는),
2) -주시 endings (for example 찾아주시면서/찾으시면서 and 말씀하시였다/말씀해주시였다),
without change of the verb meaning (im my opinion).
Anyway, does the -주 ending change the meaning of the verb, or it just adds formality?