Autocomplete requires CPU cycles for the lookup and "jump to definition" requires an index to be built somewhere (CPU again, but also mem/disk space). Modern computers can handle both efficiently nowadays, but not a simple task back then.
Pascal/Delphi is actually almost a perfect language to write a smart editor around: the grammar is highly regular and requires minimal lookahead to parse, and definitions always precede usage.
Next 3 companies I worked for were using Delphi 5, despite Delphi 6, 7 and 8 existing by that point. Same reason - if it isn't broken, you don't need to jump to the next best thing.
Also worth noting - the company I directly worked for after the one above was a Borland partner in the UK and Borland outsourced training and consultancy to them (I was under Borland NDA) and we therefore had access to pretty much all the Borland software (I have a copy of the first Kylix Beta somewhere still I think)