The reasons for using Battlemechs are actualy quite variegated in the Battletech Universe.
Conventional vehicles like hovercrafts, tanks and wheeled vehicles have a narrow bandwith of missions they are specificaly designed for and will fullfill at maximum efficiency.
Think of how varied battlefields on a single planet like earth can be....now imagine taking an army into space.
A tank can be a combat tank to fight other tanks, an arty piece or an infantery carrier or even a mobile anti aircraft weapon.
Their prefared terrain is specified through their manner of locomotion.
A tracked vehicle preferes dense sand/earth or grassland and can be quite heavy but also gets problems in swampy, broken or asphalt territorry.
A wheeled vehicle preferes streets or comprimated earth and tends to be faster than a tracked while not beeing able to carry as much load and being more vulnerable to weaponsfire regarding its locomotion system.
A hovercraft is quite fast and will be able to scim earth, sand, swamp or see but is vulnerable to weaponsfire and rocky or broken terrain.
The first Battlemechs where actually designed to singlehandedly fullfill the role of a whole tank cavalcade.
Beeing able to use their hands to clear debris or carry loot while also beeing able to cross terrain a tank would get stuck in like dense woods, broken mountain ranges or the ruins of a city.
The main reason for this uncertainty of mission profiles was simply the size and variety of possible battlefields in the early sparsely settled inner sphere.
A Battlemech also does not require a lot of tech crew or operating crew compared to a squad of tanks.
Less Humans mean a lot less tonnage and space that has to be transported through space.
You now may ask ... "why not just use drones or KI?"
Simple... drones need a com line that would be much to slow over interplanetary distances...not to speak of interstellar distances or the opening for highjacking or sabotage.
And KIs are notoriously bad in unknown situations because of their inherent lack of creativity.
So what to do?
Use something that is as mobile as a human while beeing able to absorb more damage as any tank could and beeing able to operate in all environments from the vacuum of space to underwater.
You now may also ask..."what is with all that oldschool equimpment like cannons and unguided rockets on fusion driven spacebots?"
Again a pretty simple reason.
They work. No matter what.
Try to use a radarguided missile on a planet with electromagnetic storms, on asteroids orbiting a pulsar star or in the sandstorms of a desert planet.
Try using heat seeking missiles on Vitric forge.
Try using laser guided missiles in the snowstorm of Frozen colony....OLOLOLOLOOOL.
Non of Battletechs standard missiles are target seeking or even target following they are all primarily source guided by their firing unit.
There are actually are high a number of strategic weapons in the BT Universe that are guided or even robotic in nature.
It is just that their size is on a an other scale.
It begins with nuclear armed cruise missiles (just the space kind) and ends with interstellar drone warships.
It's just that all the Houselords in the inner sphere used those weapons freely in the 300years after the fall of the Starleague....resulting in a crucial loss of infrastructural and technological capabilitys of all war participators leaving just the most rugged and versatile weapons behind letting those break down that require a lot of supplys or complex asortments of spareparts and maintenance material.
Most nowadays people are to cought up in the asymetric battles faought by US military to realize that all that fancy toys are actually pretty useless as soon as somebody comes along with either the same or a better tech level...or just an military doctrine that seems alien to them.
A F25 is nice but what if their enemy simply does not use radar to detect it but rather orbital infrared scans that lock on to their exhaust fumes....
What if its enemy does not even need to be made of vulnerable radar absorbing materials but is made out of foamed molecular crosslinked titan-steel-carbid and is shielded by an 300MW Fusion powerplant driven ECM?
All its fancy detection electronics, its stealth and all its guided weapons would be absolutely useless against such an adversary.
Remember that most weapons only work properly when they are used against the foe they are designed to be used against.
A heavy twohanded longsword is a good weapon when you are a Knight fighting against a slow heavy armored Knight....but the Longbowmen may just run and shoot right through your armor from afar.
Edited by The Basilisk, 04 January 2018 - 03:28 PM.