Rational behaviour entails making decisions or taking actions that result in maximising utility or satisfaction. The time value of money dictates that the opportunity cost of foregoing earning potential today is the interest accrued on the savings for future use. A rational consumer who wants to maximise utility will always take the $2,000 dollar cash back since the implicit interest incurred by taking the 0% financing results in a lower future value (in 5 years).
A change in interest rates is one way to make that correspondence happen. A fall in interest rates increases the amount of money people wish to hold, while a rise in interest rates decreases that amount. A change in prices is another way to make the money supply equal the amount demanded.
As the name suggests, convenience products are made for people's convenience, and so it is not surprising to note that they must be in relatively high demand. This high demand for the product means that there is the possibility of running low in supply if the current available stock is not enough to meet the demands. Therefore, having these products in stock regularly and consistently can become a primary distribution concern indeed.
Currently, most people can simply decide to skip ads. When you hire streaming services like Netflix or Disney+, one of the advantages is that there are no ads. People now watch the ads that they like and want to see, unless you are stuck watching the Superbowl or some type of live event. This adds pressure to marketing campaigns since ads need to attract viewers.