I mean, if someday Cassie was forced to go one on one with Visser three, wouldn't she prefer to have the strongest morph possible?
i think that harks back to cory's original thoughts: the wolf is useful for stealth and adds to the team's tactical battling flexibility, but cassie had many opportunities to add to her repertoire and nothing, in particular, was stopping her from doing so.
the one argument that i've seen for the "let's not acquire ____" in any context for any animorph is "what if there's a limit to the number of morphs we can acquire? then - murphy's law - when we really need a morph, we won't be able to acquire it", but that really never stopped the animorphs. when they wanted/needed a morph, they acquired it.
another argument is that cassie might be reluctant to morph at all because of the whole 'animals are people / are we yeerks' conundrum. while cassie speaks occasionally to this, she frequently acts contrarily to that hypothesis in her role as 'morph expert'. she willingly and without reservation supplies animals for the animorphs on a regular basis. she also doesn't hesitate to morph when the group needs to morph and she stays in morph as long as necessary to get the job done. so while i think that cassie may be reluctant to acquire and use morphs, the all-encompassing theory that she wants to avoid morphing (period) doesn't completely gel.
perhaps the specificity in the grey area is in the nature of the morph. cassie chooses a morph that inflicts damage and gets the job done... but can the wolf take out, for example, hork bajir with the same efficiency as a tiger or a grizzly? i suggest 'no'. i would also suggest that other animals (cathey's suggestion of leopard) might provide the same flexibility in battle and with greater efficacy than the wolf. why, then, does cassie not find and acquire those animals?
i'd have to re-read #19 (or rytx, the living animorphs-ionary/-asaurus, can beat me to it), but i think that there are times when the animorphs can't or shouldn't acquire morphs, even when they're available. for one, coming out of a life-or-death situation, they might not be in a mindset to acquire morphs. also, even if they have presence of mind to say 'a-hah! new morph!', their pausing at those times to acquire a new morph would add time and risk to the mission. it
really wouldn't be appropriate, at that point, to stop to shop for morphs. implicitly, i think that they understand that. i don't, however, think that the animorphs
never have a prime opportunity to look for or acquire new morphs. why, then, doesn't cassie take advantage?
anyway. i would suggest that cassie tries to limit her casualties by sticking with the wolf and that, because there's no serious detriment to the group because she does so, it works for the animorphs and for the series as a whole.
...argh. more thought-tangents before i can even hit the 'submit' button. anyway- cassie's decision to stick with the wolf (and the animorphs never really questioning it like i think that any of them actually ought to have done at some point and for the same reasons) might have been an effective way for katmike to communicate cassie's nature to the audience.
because hell, if i was jake, i'd want to hook my not-girlfriend-girlfriend up with something bada*. ditto the others, simply because it helps the team for individuals to have beefier morphs on hand. ...of course, when you're 13, do you really think about these things?
(no. i can answer that. i would have. xD)