Not too bad of a life? Lets see...
The majority of racehorses are stalled or in sand rolls at all times when not being ridden or worked.
Horses are designed to be moving and eating constantly - Their entire body is created to function under these conditions - Depriving a horse of movement and constand forage is really, really bad for their health. Will go into more details in the next bits.
Racehorses are fed huge amounts of energy rich feeds - usually grains, which means the feed is also super high in sugars and starches.
Sugars and starches are NOT GOOD for horses. They cause Cushings, IR, Laminitis... They are not designed to digest grains, but forage - I won't go into details but digesting grains alters the acidity of the gut and also leads to a huge spike in blood sugar.
The majority of racehorses are shod.
A shod hoof physically can not function how it was intended - The digital cushion and frog are designed to absorb shock, turning it into heat enegry in the blood and diverting it sideways via the lateral cartilage and facilitating circulation. A shod hoof lands toe first and the shock absorbers dont' even touch the ground - So all shock travels straight up the hoof wall and into the joints which have no protection against concussion. These horses are asked to gallop flat out on a hoof that isn't functioning and is directing concussion straight into the joints. Hence s many ex racehorses have soundness issues.
Need I go on?
I don't believe the entire racing industry is evil, and I do know there are many trainers and owners who do the best by their horses. I have worked at a training stable. However I don't for one second think that racehorses have a good life.