Strength of schedule is a subjective thing, and subject to change as the season goes along, and teams expected to be strong unravel while others thought to be down surge. But its importance has increased, most notably for those teams that are in competition for one of the 4 berths in the College Football Playoffs. We've all read about Baylor being penalized for 1 loss to a good team because of having some of their wins being over not so good ones.
It's also important if you are jockeying for the Group of 5s berth in a NY6 bowl game, or in some cases, the Holiday Bowl instead of the Las Vegas Bowl.