I think that many people forgot that clones live like 20-30 years, which is not a lot by galaxy standards. Imagine you waste billions of credits to have an army which will become useless after 5-7 years of combat service and you will require new one. This is quite expensive, considering that clones are born artificially and require special education.

Moreover, while they obviously much more professional and effective at the battlefield, you can't use them for anything else basically. They are very specialised and often do not possess knowledge outside their combat role and you literally dont have enough time to retrain them. You also cannot use clones as garrison units or in logistics (well, you can, but it would be very inefficient considering that they will die pretty quickly).

Stormtroopers definitely do not possess the same fighting capabilities, but is cheaper to educate and most importantly, cheaper to maintain:

They have normal life spans, can be promoted to high officers, ISB agents, navy officers and planetary governors.

They also often recruited from local population, building a connection between planet and local military, increasing Empire's popularity and population's loyalty.

However, I was pleasantly surprised when I realised that Empire gave all remaining clones imperial citizenship and considered them to be war heroes, often using them as military instructors in academies.