Bugs are a function of number of engineers, features, moving parts, and significant lines of code.
No-code takes out engineers, moving parts, and SLoC from the equation (as far as the enterprises buying these solutions are concerned), but leaves a lot to be desired in terms of feature set; low-code brings down number of engineers, and SLoC, whilst providing flexibility in terms of bespoke feature sets.
Also, another reason is, in essence, No-code and Low-code are natural extension of the cloud computing model in which capex is traded away for opex. And economies of scale, over time ensures, Low-code / No-code is going to be cheaper yet more reliable than anything one (tech-enabled) enterprise can roll on their own.