Why Swap with Collar?
This page elaborates on the Main Use Cases for Collar given in the Introduction.
The 3 primary reasons one may want to swap stablecoins are for yield generation, insurance, or liquidity purposes.

Yield Generation

Just like any kind of lending, stablecoin-stablecoin lending has the ability to compound yield. An investor can deposit their stablecoin portfolio into a protocol and receive supply interest and also receive borrowed tokens that they can deposit into another protocol to multiply that yield. Investors and lending aggregators can use this to generate yield from their asset pools to great effect, but they need to be concerned with 2 important factors when choosing a protocol to borrow stablecoins with: capital efficiency and protocol-specific price risk.
Capital Efficiency: The greater the LTV, the greater the yield.
Collar maximizes LTV by having no over-collateralization.
Protocol-Specific Price Risk: The greater the (floating) interest rate, the lower the yield.
Collar has a fixed interest rate that is not vulnerable to manipulation.

Insurance

Lending aggregators, whales, retail investors, and institutional investors all have a need to hedge against the de-pegging of stablecoins in their portfolios.
Passive retail and institutional investors (especially those acting as a bridge between DeFi and traditional finance) have the need to insure against price collapse and want to be able to accurately forecast their portfolio value.
Lending aggregators and whales pursuing high-yield strategies have different needs. In bull markets, the changing yield available from different protocols requires them to rapidly change their stablecoin portfolio composition in order to participate in the protocols offering the highest returns, which opens them up to price and systemic risk from the assets they hold. In bear markets, investors retreat to stablecoins (as a basket of stablecoins can be regarded as a portfolio of USD equivalents) and both the risk of de-pegging and the need for liquidity to avoid margin calls greatly increases.
Collar allows lending aggregators and whales to maintain their initial position when changing their farming strategy with a fixed cost and predictable risk structure. Collar also acts as insurance against de-pegging and provides liquidity in exchange for already de-pegged assets.

Liquidity

Stablecoin protocols themselves may incorporate stablecoin-stablecoin lending as part of their liquidity and price stability mechanisms.