Helps only until a certain point and then becomes counterproductive if they don't really like the work but can't quit due to these golden handcuffs you put them in. It could even make them disgruntled, the opposite of what you wanted. Or another possibility at an extreme end, they might even consider early retirement - happened at waymo apparently.

there are diminishing returns on salary increases. you should aim to be competitive but if you raise it too high then people will stay just for the salary. their motivation changes and they can feel trapped or just start coasting.

if someone comes to you with a competing offer, you should be open to negotiation (provided they have done well in their recent perf reviews)

It can't be all just increases in salary, but don't ever stop increasing salary. You should have a cost of living adjustment, in line with the BLS regional CPI-U index for the last year, as a minimum, and maybe an extra 1% just on principle.

This bare minimum will keep you from coming across as super-cheap and out of touch / unconcerned with their compensation. Remember most employees can get a bigger raise by switching jobs; your salary increases shouldn't make a point of making that obvious.

True, good point. I agree with the other comment though that it should be at least increased slightly.