Because back then you had to care about the differences of e.g. 16bit vs 32bit datatypes & instructions, hardware limitations are not known to modern grown-up dev people - they think hardware is unlimited. Earlier you really had do understand what you were doing, today cou can get along with a prompt - which works great, until it doesnt. Not to blame any vibecode hobbyist here, though real application development usually required some degree of deeper understanding back then.