Back when I played (years ago now) you'd find a variety of servers with different skill gain rates - some fast, some low. Some had higher total skill caps, allowing you to max out more skills, and a few had skill caps closer to the (generally considered very low) OSI standard. Some would ban macroing, some wouldn't. My understanding is that people macro'd because they weren't gaining skills as fast as they wanted to, or because the things they were macroing were really repetitive (mining, crafting, fishing...). With mining you generally had to mine a shit-ton of ore, smelt it all into ingots (losing some in the process), and then craft a shit-ton of the same item out of it for maximum skill gain, and then sell them all to NPC vendors, repeatedly, because it's not like you're going to find ~100 players per smith who want to buy every craftable item that's on the path to maxing out smithing, especially with every smith going through the process.
The whole reason those hotbar abilities with cooldowns are popular is because they give you something to do in combat. In UO you double click your target and your character does all the work for you, unless you're an archer (then you kite them while your character shoots for you) or a mage (then you kite them and press macro keys to cast spells, which you set up previously, which is more like other MMOs except you're using mana - or if you're crazy you can try to kite and at the same time try to double click spell buttons you've placed on your screen, and then try to click your target. This is why the game has (simple) macros built in.).