It was introduced in the 60s to compensate for the away travel offset and differences in pitch quality I assume, not sure those issues really exist in CL with millionaire footballers travelling on private jets so guess makes sense.
Would be interesting to know just how many ties we have won on away goals in the last 20 yrs. Can’t think of too many interms of big games immediately, only the Barca one back in 2007 comes to the mind straight away