How much juice does a motor use at different speeds

I am guessing that an electric motor uses less power at a slower speed. I am new at this so be kind...

If it does, why does everyone use gear reduction? Why not just program it to run slower and use less power? Its not a gas motor that only develops torque at speed.

Check out this page: https://www.ebikes.ca/tools/simulator.html

There's a cool tool that many of us, here, use to figure out how much power we need for various speeds using different bikes and motors. Various factors come into play. Basic physics knowledge will come in handy. If you remember that drag is your main competitor at high speeds (to the tune of the square of speed), you'll notice that the simulator understand that as well and models it well.

Read the page and play around with the simulator. You'll also notice that not every motor is the same, nor is every bike. And although not every motor is listed there, it will give you a better understanding of how much motors use at speed.

Play around with this simulator. Put the human power at 0, click simulate, then try different throttle percentages or grades. At the bottom pay attention to battery power, motor power, and efficiency.

https://www.ebikes.ca/tools/simulator.html

Edit: beat me to it.