JK takes an aspirin a day because it reduces  

the leading form of cancer 

COLORECTAL CANCER 50%

PANCREATIC CANCER 53%

LUNG CANCER 33%

ALZHEIMERS 35% to 52% for equine estrogen,

PROSTATE CANCER

 breast cancer 20% and C-section 400%

Cuts in half the level of C-reactive protein

And it reduces the risk of heart attacks 20-25%

Stomach bleeding is greatly reduced by using coated aspirin. 

In properly controlled, fair studies the risk of stomach bleeding is about equal.  And for the low dose in prophalitic use, (not the much higher does for pain management) the risk is slight--about, less than one per year per 1,000. 

Goodman & Gilman, 11^th Ed. P. 690:  “Although aspirin is regarded as the standard against which other drugs should be compared for treatment of rheumatoid arthritis, many clinicians favor the use of other NSAIDs perceived to have better gastrointestinal tolerability, even though this perception remains unproven by convincing clinical trials.” 

{As I pointed out, most test use a a low does of a coated NSAID compared to an uncoated aspirin.--jk}

It has come to light in 05 that all the NSAIDs but aspirin increase the risk of heart attacks and strokes by accelerating the rate of plaque formation (viz. arteriosclerosis)—a fact few doctors are aware of.