Explain why the relationship between how much steven charges and time is a promotioninal relationship

Yes, because the more time steve takes working on whatever he's doing, the more it promotes him to delay it so he can charge even more, like a car mechanic, the longer time it takes they more money they make, so they feel promoted to stretch while picking their teeth.

unless you meant, proportional.

say for example Steve charges $5 per hour doing some work, in 1 hr, he chargers 5 bucks, in 2 hours, 10 bucks, in 3 hours 15 bucks and so on.

the amount being charged, is increasing by a proportion of 5:1, for every 1 hour, 5 bucks, so is a direct proportional variation type of relation.