Test is best because many men can tolerate it well. It is bio hormone after all so body recognizes it easily. It is also the most studied steroid and considered the safest overall. There isn't all in all more completed drug therefore it is for a reason TRT (Testosterone replacement therapy). If there were something more suitable I have no doubt it would be pushed. But there isn't.
It's not just about being the biggest bang for the buck or providing insane gains kinda thing. You have to consider everything it has to offer.
Overall, you won't find anything as sustainable as Testosterone long term. It can be used for a cycle or trt. If used correctly it won't ruin your health. Side effects are well known and quite easy to manage at the end of the day, compared to 19 nors or other less known/exotic stuff and so on.
Availability and price is perhaps a factor too, but it's not because of people not having enough money, rather it is more so that the price is right and the ester choice makes it an excellent steroid for almost all people, ranging from short to mid and long esters there is a suitable version for everybody.
Finally, I just view it like it is a reliable work horse that is not replaceable. It is a male parent hormone, male hormone replacement drug, a base for every cycle, a powerhouse if dosed high. Without it? It's not really sustainable long term and that is the key.