It's like a trip: first you look at the route on a map of the country, then you look for the right turn on the street. The other way round doesn't work: from one street you can't tell which way to go.
An example. Say that on the 1Y scale an asset is in an uptrend. On 1W the price has been falling for several days and has reached support. On the big scale this is an ordinary pullback — a short move against the trend inside the trend itself. The spot at support is a convenient place to buy in the direction of the trend.