Influx

Everyone has heard the statistic that ninety percent of new products fail within two years of release. Even huge brands with enormous R&D and market research budgets release unsuccessful brand spin-offs every year or two.

One scenario is that the company releases the new flavor or model intending to win lasting market share but the public just sees the spin-off as the latest thing, something to try and then move on to the new latest thing. The slump in sales of Mountain Dew Code Red and Vanilla Coke speak to this phenomenon.
Article about slump in Vanilla Coke and Mountain Dew Code Red sales

Another scenario is that the spin-off models and flavors are released purely for halo effect: for the attention and ambiance that spill over onto the original brand. In this light, they are essentially fashion brands, periodically releasing new variations, many of which are probably not even meant to win enough market share to survive very far into the future. The PT cruiser, for example, had a rejuvenating effect on the Chrysler brand by putting the original brand back on some otherwise unacquainted consumers’ mental maps.
Article about fashion models in the auto industry