well... first things first..... just because you have a no/n at the end it doesn't mean that you are giving a reason..... all it really does is soften the sentence... just because you have the no/n, it doesn't mean that you're giving an explanation or you're not required to give an explanation....... and really when i use the structure myself.... it is usually when i write letters to friend usually involving some sort of persuasion..... usually you are required to do these in the extended response and the second writing task....... i use it because it will soften the sentence therefore sound more convincing and persuasive...... and it's best to use plain form in these occasions..... if i was to give an eg....... say you have to convince your friend to go to a japanese cutural centre with you..... i would include stuff like 'maenimo, konoyouna kyanpu ni itta koto ga aruyo~ hontouni yokattaNdayo... dakara kondo ni, kimi mo ittara iiNdakedo" --(i went to these kinda camp before and it was really gud~ so... i think it'd be gud if you went as well" --- i used it twice just then... mainly to soften the parts where i am expressing my thoughts and wants... it kinda emphasises that part and in this case it emphasises that "it was good " and "it will be good" and this kinda sounds more convincing~~~ anyway~ my thoughts~~ thank u for reading~