10,000 feet? - no way I'd launch that without a tracker.
As to what point do I use when deciding to use a tracker? - that's complicated.
It depends on a lot of factors, not least of which being - do I have a tracker available and will it fit in this rocket? Other things include: landing area (vegetation/terrain/etc.), wind and cloud conditions, how complex and/or expensive the rocket and components are, tracking smoke (or lack of it) for a particular motor, and certainly expected altitude.
On a clear day, with the sun NOT in a position that it might blind me, I can generally track a rocket visually up to 5000-7000 feet, sometimes higher. But there is no way I can guarantee it. And then, it can still be VERY easy to lose visual lock on the way down. So, even though I can probably get away without a tracker on a flight like this, I usually use one. And it's saved my rocket many times.
Most of the time, if I'm flying above about 2500', I'll use a tracker IF I've got one and it fits.
If it's cloudy - use a tracker. If it's really windy - use a tracker. If I've got a lot of expensive paraphernalia in the rocket - use a tracker. If the landing area is bushy or high relief - use a tracker. If the motor has little to no tracking smoke, and/or is very "fast" - use a tracker. If I've got a tracker just sitting there and it fits easily into the rocket - why not?, use the tracker.
All that said, I still fly the vast majority of my flights WITHOUT a tracker. That might sound surprising given what I said above, but there are other factors. First, I fly a lot under 2500'; most of these rockets are simple motor eject and I just want the simplicity of launch/recover/repeat. Second, even for flights of 2000'-4000' or so, most of the time I "know" where they are going to land, and once I start flying for the day I can generally keep an eye on things quite well. Lastly, a lot of the time I either don't have a tracker available, and/or the rocket won't fit or carry one easily. So, you certainly don't NEED a tracker to fly and have fun.
But it sure is nice to have when you do. And you WILL be glad someday when you recover that rocket that would have been lost otherwise (which is pretty much a guarantee).
s6