Why are modern day elements so normal for the people in the ancient realm? (and vice versa!)

Currently watching the show for the first time and i'm on episode 37 so maybe it gets explained at some point or maybe not. But the first time Miroku gets introduced, he casually picks Kagomes Bicycle and rides it. How in the hell has he ever seen a bicycle and how does he know how to ride one. And thats just one of many points. The only time this clash gets adressed is when kagome appears in the ancient realm for the very first time and the villagers and kaede get to her. After that its like the entire show expects everyone to act normal that this girl in modern day school girl uniform with a bicycle is just a normal part of the world. It seems that it has not even been that much of a surprise for Inuyasha to hop into modern day japan either when he tried to stalk kagome out of jealousy (right in the koga mini arc).

Ive also never seen kagome to be surprised or traumatized to see giant demons or even dying and killing people. But my headcanon tells me its cause of her being a reincarnation of kikyu