Because you, without a business model, claim you have a way to make the highest guaranteed yields in the history of mankind yet you want other people money to do this.
1% return a day means you double your money every 70 days, so after a year you'd go from 1BTC to 32BTC, and by the end of the second year it'd be hundreds and hundres of BTC. By the end of the decade you'd own every BTC in circulation.
Even with the most elaborate business model, there's a chance it could be a scam regardless so it doesn't matter how enticing a proposal may sound. In the end, it comes down to risk. As the saying goes, "No risk, no glory", but I'm not implying people should risk into things blindly. Everyone should practice self-diligence and do their own homework and not risk more than they are willing to lose. My yields are not guaranteed which is why I'm offering coverage for the investment.
You calculation for ROI is sound but only in a perfect world which doesn't have external factors limiting the outcome. Sort of sounds like a BTC calculator, people who don't understand how the market operates tend to believe the monthly ROI is set in stone and that is how much one will make. Regardless, the yields I'm offering is high because this is a start-off. If/when I create a positive portfolio for myself, it's only natural that the yields will fluctuate.