I happen to work for a very large car company as a manufacturing engineer. No, we don't do this deliberately, and as said below, we don't not do it deliberately, either.
Our number one goal is customer satisfaction, and if you Pareto it right, the vast majority of customers don't service their cars themselves, and have no interest in doing so. They're more satisfied with fit-and-finish, safety, economy, and features that will delight them. If it were the case that 80% of our customers valued home-serviceability more than these things, then designs would shift towards these things. It's simply not possible to make every, single part easily serviceable given the demands of the modern designs.
There's not a single powertrain engineer that says, "Hey, let's put this air intake over the number 5 cylinder so that the customer will be discouraged from changing the spark plugs himself at 160,000 km." Instead it's, "Bummer that this air intake is in the way of the number 5 cylinder, but I have to route it here because the cabin air filter, goes here, the oversized washer tank goes there, and I have to figure out how to package the rest of the components, too."
And modern cars require less service. I used to have to change the points in my VW when I was a kid, every 3000 miles if I recall correctly. These days as long as you change your oil and filter every 10,000 miles, you don't really have to do anything else. Home serviceability is still possible, if inconvenient, but it's more than offset by the larger service intervals.
For other routine, at-home-typical tasks, there's not a huge barrier versus the past. Brakes, filters, oil plug, are all nearly as simple today as they were in the past. Maybe the alternator or water pump is hard to get to, but then again, you're not replacing these every 50,000 miles like in the past, either.