You smell bad because of your diet.

Build up of aromatics in your adipose tissue that are released over time via your sebaceous glands, bacterial decomposition products of those compounds, and off-gassing of bacterial decomposition byproducts from your orifices contribute to bad body odor.

People are different and skin biomes can change. The ways that showering habits (frequency, duration, temp, ph, soap use, etc) effect skin biomes is poorly understood. The largest factor in body odor is the bacteria living on our skin, so it is entirely conceivable that with a different showering regime your skin biome would change over time and cause you to generate BO differently.

Not only from just existing, but between going to the gym a few days a week and doing regular cardio on other days, I just can’t imagine the absolute rank stink from not showering regularly. Once I thought I didn’t work up enough of a sweat weightlifting in the gym so went to bed when I got home, and the bed smelled like absolute trash the next day and neither me nor my partner could sleep there again without washing everything.

Maybe it’s just my neuroses or mental illness, but I can’t imagine smelling so badly and not showering even if I didn’t socialize with others, and can’t imagine I’d have many people to continue to socialize with (in USA so this is probably different in the OP’s country) if I smelled so bad when I went out.