We consist of organic matter; we’re basically meat, which spoils and decays.

There are so many ways to answer your question.
1. Because all organic matter decays.
2. Decay is necessary for recycling of finite earth resources. Ashes to ashes and dust to dust.
3. Once you stop breathing there is no oxygen in the body to keep cells alive quickly causing cell lysis( death).
4. Our bodies are actually under constant attack by fungi, bacteria etc but its only because we are living that we can fend them off.

To complete the cycle

Everything needs to decompose in this world,otherwise there would be no place on earth to fit all the dead bodies...

If you're talking about why there is a process of decomposition "biologically",I can tell you that the body of any living being human or animal,that once the blood circulation is cut off due to an incidence (death) there won't be electrolytes that give the body it's Oxygene preventing organs,blood,to rot.

it is the way of nature. all things decompose, unless removed from the biological world
microbes and fungus just doing their job

The left side of body goes to Alabama & the right side to Tennessee

Because we’re organic matter

no oxygen no blood flow bacteria its life ash to ash and dust to dust

You can put it in a freezer and save the husk but nobody would want to be reborn into that ugly bag of water.

It's how unclaimed or unpiloted living material travels through time.

Because our physical bodies are made of meat and meat rots.

Not difficult to re generate if you can get a male and female to agree not to murder it.

Would you want to unearth faces when you start a new garden?

To feed the maggots