Maybe because he is better able to focus in his local shul.
He may have a closer relationship with the rav at his shul, or have more one-on-one attention.
He may have less distractions.
The local shul may be closer to home and more conducive to the other parts of his life.
He may feel more comfortable at his local shul, which may come with less pressure than learning at his yeshiva.
Many reasons…