Staying within the same chain (in the US, they all have a broad range of properties at various prices, low to high) is very much the same as renting your car from the same franchise, using the same airline for the miles and a CC like Amex or BofA that gives you double miles and other perks (but be aware of your fees). I suppose that if you only travel once or twice a year then grabbing the lowest price you can get seems like a good idea, but when you are on the road a lot, building air miles, hotel loyalty perks (Executive floor access, free food and drinks, reserved parking, free ramp parking, etc.), access to your chosen airlines lounge with free drinks and snacks rather than sitting in seats picking up everyone's colds, picking up free/reduced/upgraded rental cars when on your *own* vacation are all part of the strategy.
It's a bad strategy unless you're essentially cooperating with the airline to embezzle money from your employer for yourself in a very inefficient way. I personally would have ethical problems with that. The airlines and other companies have those programs to encourage brand loyalty, so that you'll go with them even when they're not the cheapest. They think the cost of offering these discounts will be made up by stupid or unethical people buying tickets with them even when they're not the best choice. It works; otherwise, they'd cancel the programs.
There's no "long game" with airline perks. Sure, get an account; there's no downside. But, once you have an account, try to get rid of your miles as quickly and efficiently as possible. Don't hold onto them; the airline can and will devalue them eventually if you do that. And don't take a trip on a particular airline to keep your miles from expiring or something unless you really calculate it out: the value of your miles is, if you're following this advice, almost certainly less than the value of the difference in the ticket. We're talking about maybe $150 worth of company credit here if you have 15,000 points on Southwest.
Of course, if you're a frequent business flyer paying $3,000 in extra airline fees on your company credit card so you get to go to Hawaii once a year and eat free peanuts before your flight takes off in a private lounge, well, again, that's called embezzling, and you're a thief. But I guess it might work out for you in that case if your company never does internal audits.