A lot of cats die every year from [Cytauxzoonosis](
https://en.wikipedia.org/wiki/Cytauxzoonosis) (aka "Bobcat Fever"). It's absolutely terrifying disease which kills the victim slowly and with an extreme amount of suffering.
This horrible parasite killed two of my cats this summer. I've learned that it has become very common across a large part of the US and is spreading rapidly. The vet in my small town told me they saw at least 35 cats so far this year with only 2 survivors. It seems to have wiped out most of the feral cat population in my area in a single season.
There are some treatments but they are both expensive and fairly ineffective. To make things much worse, survivors become carriers of the parasite and can then infect ticks which go on to infect other cats. If all of that wasn't bad enough, you may not notice anything is wrong until it's far to late to do anything about it. At first, the parasite multiplies quietly for several weeks. By the time there are noticeable symptoms, the cat has only a few extremely miserable days left to live. The treatment is only effective if you catch the disease extremely early which is unlikely unless you (your vet, more likely) proactively examine a blood sample under a microscope to see the parasites. It's easy to miss them during the early stage of the infection when their numbers are small, so the test is non-conclusive. This is obviously not practical or economical.
I'm also unsure if the parasite can be avoided by judiciously removing ticks. It may be like Lyme disease, where you can prevent infection by removing the tick within a short time, however, I haven't seen that stated anywhere. It's a parasitic organism similar to Malaria, unlike Lyme (which is a bacteria) I'm not so sure you can count on any time delay before infection occurs.
I guess what I'm trying to say is, treat your yard for ticks. Watching your cat die from this disease is traumatic and heartbreaking. I would not recommend it to anyone.
As if all that weren't enough to think about, one more warning: If you deploy a pesticide to control the ticks, it's important to know that the most effective chemical is permethrin. Unfortunately, it's highly toxic to cats. Just a tiny amount of the stuff can be deadly. Humans and many other mammals can break down small amounts of permethrin without difficulty. Not so for felines. Any amount of the stuff is really bad for them and this is why some cheap over the counter flea collars make cats sick. This further complicates the situation. At the very least make sure that your pets are inside for a while after applying any chemicals around outside.