Tighter margins, sharper tests
At the front of the field, a dominant car can sometimes mask small inefficiencies with sheer pace, but in the midfield, where several teams are separated by fractions of a second, those same inefficiencies decide whether a car qualifies eighth or fourteenth. This makes the midfield a more sensitive test of a team's day-to-day execution, since there is far less pace in hand to cover for a mistake.
Points that matter more than they look
Points scored outside the podium places still carry real weight, both for the constructors' championship's financial rewards and for a team's ability to attract sponsorship and staff. A midfield team fighting for sixth place is often fighting just as intensely, in relative terms, as a front-runner fighting for a win, even if the broadcast attention is not proportional to that intensity.
Where development gains actually show
Because midfield gaps are so tight, a genuine step forward in car performance shows up immediately in relative position, whereas a front-running team's true progress can be obscured by how far ahead or behind its closest rival happens to be. Watching the midfield closely over a season is often the clearest way to see which teams are actually developing well, independent of who wins on a given Sunday.