Inefficiencies are a sign of incorrect modelling.
Inefficiencies are a sign of slack coding standards.
Inefficiencies are a sign of not knowing exactly what the code is actually doing.
Ultimately, these all lead to errors, and when compounded across multiple running programs, will have effects that are neither predicted nor likely to be desirable.
Your model is good:
Is it slowing down the users?
Are we getting hammered by the electricity bill?
Is the machine getting tired?
However, it lets dirty code slide into use as long as you can say, "It is slowing down the users, but they will never notice and besides, our electricity bill is not rising too much."
Like the real Donald (Knuth) said: "premature optimization is the root of all evil (or at least most of it) in programming".
The keyword here being "premature". Do not take it to mean optimization should never be done or even that optimization is unimportant. It is merely stating that getting optimization done before you have everything fully modeled out is a waste of time (for various reasons).