John Chrysostom

Then after this, Mark, who delights in brevity, to show the nature of the parables, subjoins, And with many such parables spake he the word unto them as they could hear him.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

The Lord speaks to the people in many parables, offering parables suited to the condition of His listeners. Since the people were simple and unlearned, He therefore reminds them of the mustard seed, of grass and seed, so that through things familiar and ordinary to them He might teach them something profitable or cause them to approach and ask, and through their questioning understand what was unclear.

Commentary on Mark ↗

Bede

And with many such parables he spoke the word to them, as they were able to hear it. But without a parable he did not speak to them. But privately he expounded all things to his disciples. This is not said as if he spoke no plain words to the crowds, but that he spoke to them only in parables: rather, it is because almost no speech of his can be found in which something of parables is not interwoven.

On the Gospel of Mark ↗