Generally there are a few categories of ice that you want covered. Cheap ETR, damage/tax ice, giant pieces etc… The categories of ice that you want will depend on your deck. Multiple 1x’s are good when they all fulfill the same role but in different and complementary ways.
Also your overall ice strategy has to be taken into consideration (cheap ETR, because I’m a rush deck, taxing frustrating ice because I’m an RP glacier…)
For something like a cheap ETR that I can put on centrals to prevent early access, yeah I could play 1 Ice Wall, 1 Eli, 1 Wall of Static, 1 Himitsu Bako, 1 Wraparound as my barriers, but what do I gain from that? Some marginal utility at the cost of influence.
Now on the other hand, looking at your damaging sentries here is a great opportunity for variety. 1 Archer (assuming your agendas work with it), 1 Roto, 1 Grim, 1 Ichi, and 1 Sherlock is a nice mix because they all do the same thing (remove programs from the board) but in different ways. Roto and Ichi dodge D4vid, Sherlock dodges Sharpshooter, Archer is likely to stay on the board and be really taxing, even to being bypassed by Femme or a Str 6 Atman. etc