Its based on other factors like debt to income, income amount and credit utilization.

You're off on some of your measurements. FICO scores are based on only 5 inputs:

• payment history (35%)
• amounts owed (30%)
• length of credit history (15%)
• new credit (10%)
• credit mix (10%).

source

different lenders also use different calculations depending on the type of loan.

I already touched on that with the 16 different types of credit scores: source

Underwriting is a whole career and a company doing lending that knows anything will look at how well you actually pay your obligations and weight it with how much you make, practically ignoring the score itself.

You're right that underwriting is a whole career, but we're not talking about underwriting. We're talking about FICO credit scores. You're bringing in things that aren't credit score, but are factors that lenders use for determining loan worthiness and interest they charge, but that isn't FICO credit scores.

Myself and OP are talking about the price of apples here. You're asking me why an apple pie costs so much. Yes, apples are an ingredient in apple pies but not the only thing that influence the cost of the pie.