Wonder if its related to its orbit in the lagrange point? Seems like it might make sense that lots of meteoroids hang out around there for a bit longer before drifting away.
The L4 and L5 Lagrange points are stable. Objects orbiting near those will tend to remain near that point. Well-known examples of these are the Trojan asteroids, in the orbit of Jupiter, at the L4 and L5 points of the Jovian-Solar orbit.
L2, near which JWST orbits, is an unstable point. The JWST must continuously expend propellant to "drive uphill" toward the point (it orbits nearer Earth than the actual Lagrange point). At end of life, a final burn will drive the satellite beyond the point, from which it will eventually drift into a solar orbit.
Other orbiting material similarly will fail to aggregate near the L2 point.
As I understand, the L2 (beyond Earth), L1 (between Earth and Sun), and L3 (opposite side of Earth, behind the Sun) are all unstable liberation points.
That said, plans for structures at L4 / L5 might want to consider the general attractor property of those orbits.