[intelekshual]

The variable here is overhead bin space, not seats. People want to board first, regardless of their seating assignment, so that they're assured a space for their probably oversized carry-on luggage.

[joosters]

Ah yes, good point. Still seems excessive to me, in the past they have offered to check-in luggage at the gate (for free) if they are getting full.

[M2Ys4U]

I wouldn't trust any budget airline to do anything for free. They're notorious for charging as much as they can for even the slightest convenience.