Even though I prefer firefox for my majority of browsing, I still use ie from time to time (via ie tab through firefox or the avant shell) & that deos me. If something is strictly written for ie then I will use it, as I also prefer firefox not just for the reason of msot people sayying "OMG LOOK AT IE IT HAS EXPLOITS!!!!1111ONEONE", I also use it due to how you can customize it with extensions and add features. Every peace of software known to man has exploits, find me one program that does not have a glitch, exploit or serious security whole or some other serious problem & I will be amazed.
Using Linux doesn't nessacary make you safer in all terms as it will also come down to your knowlege of computers or of the internet and how you use it. You could still be exploited by someone who finds an exploit in something. However, yes people are gonig to target the more popular products. People use IE because it comes with windows & it's because they have been using it for god knows how long, if some make the switch to some otehr browser on windows then that's entirely there decision based on what may of happened with the other program they were using or this other app they want may interest them in it's features. I for one switched to firefox because a java site crashed ie for me at some point, and mind you i'm lucky I did as my brother had to reformat that day and ie was really giving him the stuff, and if it had been spyware I may have been pwned buy it too (this was atleast 2yrs ago). I also wanted some more features for my browsing and was curious to see if it lived up to it's huge user hype.
I'll setup linux ethier on older machines to make use of them or if someone needs an operating system for free (this would be good, given that software piracy is infact ilegal, I mean sure you can burn someone a copy of windows, but then they can be locked out of updates and such and get pwned by a security flaw in some software, unless of course I showed them some good stuff to use as an alternative, but in the end it is there choice weather or not to use it, it's not like I would be sayying "USE THIS OR DIE", i'd jsut say "I'd think it would be good if you were to use this program, give it a try and see if you like it"), also keep in mind that boths linux distros and windows have there handy uses and features over one another, and to enjoy linux to it's full you'd have to have some decent know how on linux to make full use of it.