Why is most of our S.S. benefit taxable?

You said "our".  I assume you are talking about a joint return. If 50% of your SS ($7,386) plus your other income exceed $32,000 some of it is taxable. As that total increase, so does the portion that is taxable until it hits 85% taxable.  This began in the mid 1980's, but the limit then was 50%.  It increased to 85% in the 1990's (not 95%).

Social security has been taxable since 1983, when Joe Biden, our now President, voted for it!

In 198e Joe Biden and his cronies enacted a law that taxed SS 50% of income.

In 1993, Senator Joe Biden cast the final vote to increase the taxable amount from 50% to 85%.  This vote created 50 votes for and against, which led to VP Al Gore placing the deciding vote in favor of the increase.  In this single move, it decreased the spending power of senior citizens an average of $17,000 per year.

** This is exactly what you are seeing on your tax return.  $12556 is 85% of $14772.

It is based on the rest of your income. There is a worksheet within the tax return that shows you how it works.

It caps at 95% depending on all other income.

It has always been taxable in general.  Maybe your prior circumstances caused it to be non-taxable.