A single spike does not reflect poor health on the plant. Many hybrids of Phals as with other plants are crossed taking the strongest qualities/ strengths of the species plants, primary hybrids etc. The results vary but for a simple summary a plant that likes cooler can be crossed with a plant which has warmer requirements and the objective is to produce a plant that lies in between thus our growing environments become slightly more/ widely accomodating. Thats just a snippet and much more detail ,info/ factors/ reasons exist. I cannot begin to provide/ elaborate as my knowledge is not great/ sufficient enough. In addition a plant/s selected for improvement in its growth rate or be miniaturized or bloom improvements can be attempted to redesign genetics so this can be obtained. Flower shape, pattern. colour and fragrance are all relevant factors.

Many of the commercially mass produced widely available phals can easily compromise 1 lead (single) crown plant as they can also be easily 2 crown leads. Obviously the plant s that have flourished in cultivation for varying factors like nutrition, light, warmth, temp, humidity and parentage and have 2 crown leads improves its chance at increased number of spikes.

Just in comparison a single crown lead that has produced more than 1 spike can be exhausting for the plant.
Hope it makes some sought of sense!

This was posted same time as Jeffs reply and the maturity of plant also increases chance of spike numbers like jeff said