The protocol (code) is designed this way.

It is not related to block size.

An automatic difficulty adjustment in the protocol causes the time to mine a block to average 10 minutes.

In my understanding, this is to ensure that the rate of coin issuance is relatively consistent.

It's quite deliberate, part of the genius of bitcoin design. Do a search on "timechain." About every two weeks?, the bitcoin algorithm adjusts the difficulty of mining a block either up or down to keep block issuance at 10 minutes per block average. This guarantees the consistency of bitcoin inflation until the last sat is mined in 2140...😃