If you lock your ETH into a CDP - you believe that ETH will not go down. You can also take the DAI from one CDP, exchange it to ETH, and then re-invest it into another (or the same?) CDP - thus creating a synthetic leveraged ETH long position. This can be repeated multiple times;)
My point was that people continued locking ETH into CDPs during the 2018's 90% fall in ETH prices, which only made sense if they had cheap ETH (i.e. insiders/OGs), and their goal was to prevent DAI from de-pegging.
MakerDAO's CDP doesn't seems to be the best instrument for making a LONG bet on ETH. You can just hold ETH, or you can buy ETH futures on Bitmex if you want leverage.
The problem with many algorithmic "stablecoin" designs is the assumption that there always will be speculators willing to take the risk in exchange of betting that peg will be restored. But unlike the designated market makers in some regulated markets, crypto speculators are not contractually obligated to take the risk.
Users need to monitor their open CDPs and add collateral if they are at risk. This has been done to protect users from paying the liquidation penalty fee, which is ~ 13%.
Also, do you really need leverage if your ETH's cost basis is 0 to 30c at the time when market price was in the range of $141 to $816 range?
It's all rounding error to you, you can basically print DAI out of thin air.