Runaway successes like FB are outliers. Failed businesses OTOH are quite common and usually have a number of causes where bad technology choices can be at least a factor.

You call it poor management in retrospect, but it's succeeding in spite of the tools when you're still doing ok. There's a lot of companies that exist in between failure and "Facebook" who don't have hockey stick growth curves who also can't afford needlessly higher technology costs, whether that's in infrastructure or staffing or opportunity costs in getting features to market. If PHP does't incur a higher cost personally, go for it, but it might be a strategic disadvantage later if you don't hit it big.