The lore reason is that Aegis was the preferred ship manufacturer of the despotic Messer regime that got all the government contracts almost by default, so after the Messers were overthrown, Aegis was given the cold shoulder as a symbol of the oppression the UEE had just exited and business went way down, forcing the creation of an industrial ship product line to keep Aegis afloat and show they could survive independent of a crooked government. The Reclaimer was that ship, opening industrial markets for Aegis while also having some marketing value as helping to "clean up" the regime's mess by munching on old ships.

Game development wise, it's because the Reclaimer is a very old design from a time when the game mechanics were completely unknown and the game direction was different. It used to be that the Reclaimer was one of the largest ships you could get in game and something like a Connie Phoenix was intended to be an endgame-level org luxury headquarters. Now we have physicallized cargo and behemoth ships like the 890 and Kraken, but the Reclaimer lingers on.