How come nobody uses guard towers and keeps? Nobody builds them in castle age or imperial age.
Nobody upgrades the techs.

The only guard towers and keeps I ever seen were korean leftover watch towers after tower rush automatically upgraded!

imagine this, tower rushing after 40 mins, wat benefit do u get for it?

good question
why not build towers in the middle of map on arabia for example?

I'd rather save my stone for castles. They're 4 towers in one, 4x as strong (HP), more attack and can make units.

with the diversity i see of new custom RM maps being played this is a viable option,

MUST know how to use university properly, is a subsection of such skill, if/when to upgrade your towers.
in such day and age of high micro requirements and less opportunity for NEET gameplay towers can be uber effective crowdcontrol on contended/close woodlines and hyper situationally supplementary to forward 2 ranges & rax. starting positions are trending more towards the center of the map allowing for backwards boom/recovery from these forwards and the ongoing of more longer competitive games thus towers as an ongoing continuous micro investment of pressure is more feasonable/reasonable

korean tower/monk/seige spams etc
sara etc
huns etc

flushes (archers/trash/towers/forwards/palisade "laming") with farm booms & age 3 into seige/monks/knights/more towers (as your eco should be hyper streamlined unlikely to be getting NEET 650 stone drops on a 20 min FC with flush etc. towers are a more feasible incremental investment into continuous advancement/pressure/pushing from age II -> III and hence too their upgrade lines which combines nicely with your stacked archers/supplmenting your ball/providing cover to your forward melee while you wait for monk heals. it takes area of peace off the map whilst being a low micro investment high chaos return (if placed right.. skill). the tower radius is a dangerous threat until it is removed. the guard tower upgrade @ 100f & 250w in particular as both players start hitting knights and pierce armour threshholds keeps that past investment potently relevent if you have a spread 2-3++ towers covering trash and next phase forward advancement/encroachment etc/safe havens for further penetrating/raiding CA's which are hyper weak, nimble, can fall behind safety structures, are going to be requiring university investment (great forward wall building if you've got control of the area for the time to pump those early techs) anyway (or any archer for that matter).

safe forward areas for villagers/cover for seige workshops & mangonels & their afore mentioned forward repairers.

great advice is skip feudal and/or some castle eco techs instead opting for additional forward uni & techs/ whatever is situationally required/most viable, seige workshops, castles etc, then go back and get the eco upgrades (second tier stone, gold, farm techs etc - get them a phase/cycle later - opt in for forward unis instead, much more aggressive but if u can micro macro and meta in balance then i dont see why this option wouldn't or shouldn't be taken more then what i see it is..)

byz etc
pers etc

uni teching was THE thing for a while in mid 2013. its not that new i guess, just maybe out of favour.?? these guys and spanish. is the perfect out of that archer deadend spanish techball you went.. archers (with w/e age 2 inc. towers) into gaurd towers and stopping archer production.. kicking to skirms (if you need it, doubt it if you went spanish with adv into age 3 though) etc. BOOMER SOONER.
boom hard.