Yes, that's what you should expect. There's no "magic code" about upgradeability in terms of "oh, just book code Y or B" - those codes relate to Fare Buckets. They're Economy fares, but the most expensive (and flexible) economy fares. To have the privilege of attempting to upgrade with miles, you have to give United far more money for the fares.

If you have to book full-fare economy (what Y is and B is just down from there) because you need refundability and free changes, then the ability to upgrade with miles is an extra benefit. But to me, it doesn't make a lot of sense otherwise; certainly not just to be able to use 30,000 miles all of one time to upgrade one round-trip (it's 15K each way, it sounds like that's about all you'll earn.) In most cases, you are better off just buying deep discount fares, accept the occasional $150 change fees when your plans change, and enjoy E+ instead.

If you are going to fly (not earn miles from credit cards etc. but rather actually FLY) at least 25,000 miles every year, then earning UA Premier (2P) status at 25,000 EQM (Elite Qualifying Miles) gets you 4 electronic 500-mile-upgrade certificates (e500s) for every 10,000 BIS miles (actual Butt-In-Seat miles on UA-operated flights only - no partners, no class-of service bonus counts) flown after becoming 2P. You can use those to request upgrades in North America from any class of service paid coach, even the cheapest fares. Of course you're behind the higher-level elites, and as a 2P your upgrades don't clear until 48 hours out; 1P (50K/year flyers) clear at 72 hours out, 1K (100K/yr) clear at 100 hours out, and GS (Global Services - UA's biggest spenders) clear at 120 hours out. So it's pretty rare but not impossible for those free upgrades to clear. Remember you only get upgrades good for 2000 miles of upgrading (4 e500s) for every 10,000 of flying, so you can't upgrade every flight. As an elite, you can buy additional packs of these at 4 e500s for $200, rather than the "list" of $350, but you still are in line behind the higher level elites for these to clear. Also, on 319s and 733/735, UA only has 8 F seats, on 320s only 12 (or 0 if ex-Ted). So don't expect ever to clear as a 2P on those flights.

If getting upgrades to First from low fares on most flights is important to you, UA isn't the best choice for that. As a 25K/year Silver on NW, the equivalent of UA's 1P, I get upgraded on NW about 60% of the time and NW's upgrades do not require certificates. Also, NW has at least 16 F seats even on their small mainline planes, so odds are better. DL (who is buying NW) works similarly. As does US Airways, but I wouldn't wish them on anyone.

UA domestic F is better than NW's domestic F, but it's harder to get into from low fares/low elite levels.