Yes but originally Mechs weren't equated to helicopters or fighters. Originally they were directly equated to tanks and those do not have entire ground maintenance teams for every track you put on the field. What happened was that some of the people writing things decided they wanted the game to be different and started changing things. And not all of us appreciate their efforts to turn the paradigm mechs operate under from what they were to 'mechs are hangar queen fighter equivalents that require large tech crews to keep running.' Frankly I stick with the older rules on some things as I do not like where the newer versions are taking the game.
100% valid and I completely agree that not all changes have been for the better. Breaking down a battlemech from a logical standpoint though, A planned maintenance routine is going to include
Stripping, cleaning, lubricating and reassembling all ballistic and missile weapons
Recalibrating weapon aim points and fire control systems
Cleaning dirt and mud out of air filters, joints and feet
Lubricating joints all the way down to each knuckle on every finger
Connecting various pieces of test equipment to communications gear and other electronics and adjusting them to keep them calibrated
Changing hydraulic fluids, coolants and anti freeze
Testing, adjusting and logging performance of gyros
Cleaning and inspecting literally every component at least once a month
Vibration analysis
Checking for signs of stress and wear on structural components
Testing and inspecting earthing and cabling arrangements
Whatever you need to do to maintain a fusion reactor
Replace things that go out of date or calibration, such as emergency beacons or parachutes
Replace sacrificial components designed to wear out so other thing don't
Incidental repairs of broken solder joins, cracked hoses and cables, rocks stuck in places they shouldn't be
Controlling rust and repainting
And all of this before you even think about adding combat damage to the equation. So the sheer complexity of a battlemech, just at it's face value, mean that it's going to spend a fair bit of time in maintenance compared to a tank. I mean you could run them longer in the field and skip a few steps when times are desperate, but you're going to pay for it in the long run, and given the cost and rarity of battlemechs, especially around the late succession wars, I'd say the preference would be to baby them, and not take any unnecessary chances that could result in operational unavailability.