Why is my car losing coolant every day

Might be internal leakage of the engine if there is no external leak.

My first thought is headgasket, if there's no external leakage.

One easy way to check that, is to look at the expansion-tank for the coolant, where you fill in the engine coolant.

If it's brown and "gunky" and/or if it smells like exhaust it's most likely the headgasket. Since you need to fill it up on each drive it ought to smell fairly strong.

If not you can go to a workshop that can measure exhaust values, and ask them to check for exhaust in the expansion-tank.

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NOTE HERE: When checking the engine coolant for exhausts you need to do it while the engine is running, and opening the expansion-tank with the engine running can be hazardous, the lid has a safety feature where it opens in two stages, if the tank is hissing at the first stage, cover it with a cloth and wait for it to stop. When it has stopped hissing you can open it completely.

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Another is to see if it bellows white smoke in excess from the exhaust pipe.

Finally is to check the engine oil, the dipstick or the refill cap would have oil/water residue on it, the oil becomes white/gray when mixed with water and can be foamy.

These are basically checks to see if the headgasket is blown, and if it is I don't really recommend anyone to change it unless they have good knowledge of repairing engines.