Hi Charity,
They are repaying Jehovah the gift of his son The Ransom. They also believe they are saving lives. They are modern day Noah's and they are trying to get as many on the ark as possible...
Also, as mentioned when Jesus sent out his disciples to spread the good news...but here's the rub, don't know if you know some scriptures are for the anointed (too long of a story)...and some are just for us plain folk, supposedly Jesus's disciples are part of the anointed and Jesus was talking about going to door he was not speaking to us plain folks....So if the society really want to split hairs, and they always say certain scriptures are for the anointed...so, we are not anointed so we don't have to go door to door....
Going out door to door is a form of worship...JW's are work oriented....they can't accept something for nothing...Some do it because they really love it....they are outdoor people...some really do love Jehovah
There is a song in our song book that one of the lines is How can I repay you what gift can I give to thank you Jehovah for the life that you give, I think that's how it goes...
Yes, witnesses think going out in service is worship and also before all....going to the meetings...I know others here can add...
Tor