Why there’s no button switch off iPad Pro 12.9

iPad doesn’t have an on/off switch. Your iPad will automatically “sleep” when idle to preserve its battery, however, background tasks (such as regular retrieval of email - and automatic iCloud backup of data) will continue. Unless you don’t intend to use your iPad for an extended period, such as many days, it is generally unnecessary to turn-off the iPad.

If you need to fully shut-down the iPad, this is simply achieved from iPad settings:

Settings > General > Shut Down

More information about available methods to turn-off your iPad are outlined here:

Turn iPad on or off - Apple Support

newer ipads have volume up and down and the top off switch and that is it

iPad Pro - Technical Specifications - Apple

if you wish them to add more buttons in the future then you can suggest so in their feedback channel

Feedback - iPad - Apple