Convince me why I should buy the spark and pay extra for the controller.

The controller provides a much better flying experience.

Hi,

If you fly your Spark with your mobile only, you just have the Wifi distance of maybe 100m (if you are lucky, it depends also on your mobile).
With remote controller, you can fly much further away, especially in the US!
Definitely get it, its a no-brainer.
And, if your mobile uses Android, get an OTG cable (connects remote to phone to get a bit more range and lesser latency) too.

Cheers,
Wolferl

You don't have to pay extra for the controller, in case you are buying the Combo.  ;-)
That gets you also already 2 of the extra batteries, you wanna have, anyway.
After flying the bird a bit!

Hello and good day Cryptic. Thank you for reaching out and for creating this thread. Using your mobile device when flying your DJI Spark is fine. However, to maximizing DJI Spark’s full potential, you’ll need the remote controller to fly further, go faster, and generally just do a handful of very cool flying options. One of the most noticeable differences of flying DJI Spark without a remote controller is the fact that you’re limited to a distance of 328 ft ( 100 m ) with a height restriction of only 50 m ( 164 ft ). With a remote controller, the DJI Spark’s transmission distance extends to 1.2 mi ( 2 km ) while increasing the height limit to 500 ft ( 152 m ). In addition the DJI Sparks's remote controller also reinvigorates the DJI Spark’s rotors with a dedicated Sport mode switch, pushing it to a top speed of 31 mph ( 50 kph ). Thank you and fly safe always.

Don't, just buy the mavic mini.

Yep, get the Mavic Mini

Are you convinced yet?

Because flying Spark without a controller is a very silly idea.