Back in the good old days (1960s) I only changed my engine oil (condensers, rotors, distributor caps, spark plugs & wires, etc); unless there were problems I left things like tranny and brake fluids alone. Then around 70K miles it'd need a valve job. About the time the third owner pushed it to around the 100K mark it was an unreliable loose driving rusted out POS (excuse my french).
Back then it was not uncommon for folks to replace their $2000 cars at 2 (or 3) year intervals.
Nowadays a properly maintained $25,000 vehicle will easily last a dozen+ years /200K miles; part of that reason is by performing all these little things when called for.
Pay now or pay later (at trade in time).