Why do 3 months T-Bills have yield very close to S&P 500 Earnings Yield?

3 months T-Bills have a yield of 4.57%, Monthly of 0.38%
S&P 500 Earnings Yield 4.72%, Monthly of 0.39%

For the minuscule difference of 0.01% in returns I get the safety of a government backed bond. Why is that the case? Is there any point of continuing a DCA into S&P 500 at the moment?