Because Tesla is battery constrained. This will change as Megapack switchs over to LFP chemistry, and Tesla 4680 cells begin to set the price in the battery cell market.
I think this latter point is one of the most unappreciated aspects of Tesla's 4680 initiative. Whenever Tesla goes to negotiate (or re-negotiate) a price/supply contract with a 3rd party, they can say "
nice price, that's only 25% higher than our own costs. What can you do for us? 
Cheers!
What we do not know is the progress with 4680 production by suppliers. We probably can assume Panasonic might be the first one to enter production, but beyond that we have no clear assumptions to make. In any event we are probably safe to assume that quite high scaling of 4680's by 2023 will include not only Kato road, but Shanghai, Grüneheide, Austin and probably two suppliers. Well within reason might also be CATL producing not only 4680's but also producing complete packs in their new plant adjacent to Tesla Shanghai.
However this develops we can be assured that 2023 4680 battery production is quite likely to be on the order of enough to support several million million vehicles plus major ramping of energy products, probably using multiple sizes since 1680 and 2170 will be in production for years to come.
Tesla Economist, among others, seems confident that vehicle production alone will be around two million in 2022. before all this ramping.
@The Accountant has been doing excellent work trying to make longer term forecasts which also postulate enormous continuing growth.
We seem very much to be seeing continuing growth far beyond the 40% compound rate postulated by Elon. The actual factory expansions in every case are clearly anticipating unprecedented production velocity increases due to large presses, including larger and larger Gigaones. The Grüneheide paint shop, already visible, shows vast speed increases with major quality improvements as well, but with quite clever robotics that can be much more economical in use of paint and water. On top of that the famed BIW in 45 seconds.
As existing factories gradually are retrofitted speeds rise, costs go down and quality rises.
As for Tesla Energy(TE), with battery supplies rising by massive amounts in 2022 and 2023, suddenly Megapack and Powerpack and Powerwall can all ramp. Megapack starts at $ one million, so those numbers will be astounding. We cannot really assess probable margins, but with Tesla manufacturing of these products beginning to scale well, improved manufacturing will certainly begin a virtuous cycle beginning seriously in 2022.
SO all our best minds are still pretty much ignoring TE because it has not been material...yet. It will be next year. One continuing question is solar roof and solar panels. On that one I have no idea, especially since the existing manufacturers are rapidly improving efficiency and reducing prices. Maybe Tesla will not try to do anything major there, perhaps solar roof might be the exception.
SO, folks, when
@The Accountant says that Free Cash Flow (FCF) will be $1.7 billion for 3rd quarter, it seems all that cash will be deployed improving manufacturing capacity and introducing already announced TE products as well as Cybertruck, Semi, Roadster and not-Chinese Model 2, and not-German model 2. What ever those two models will be they'll be very high volume.
It is also to be noted that roughly 40% of the world's auto market has
zero Tesla presence. When we postulate growth the distribution system, including Superchargers, will require massive expansion. Thus, some of the Free Cash Flow will be devoted to vast increase in production capacity for Superchargers, plus support for other brands charging. The faster Tesla does that, the more revenues from Supercharger become relevant also. Even when Superchargers are priced to breakeven for Tesla vehicles, they'll price to profit from competitors charging. With all the growth, the sales and charging revenues will be far broader and more efficient than they are today.
From market entry terms, we may see Texas, Michigan, New York and other US States begin to life their direct sales bans. Just as materially will be filling in distribution holes in every single significant market today, including even California. Countries such as Brazil, India, plus the South East Asia, Easern and Southern Europe are all ready to support Tesl entry.
We keep having such discussion as this from time to time. Now, though, it is different. Tesla having FCF of >2 Billion dollars per quarter permits those market expansions and product broadening to be accomplished almost simultaneously. WHY? Because the battery supplies are finally about to rise exponentially next year and the year after.
