Dominion is full of glorious edge-cases. Obviously I can see picking up cards that give benefits other than trashing. Getting Steward for draw, for example. I can also see the addition of trash for benefit cards. Maybe a single trasher to activate Market Squares mid-turn. But cards where thinning is the whole point, like Chapel? They're borderline obsolete.
Sure, there are a bunch of options there:
1. Getting a cheap way to deal with junking attacks. Say you grab Followers, I can either plan to burn $8 on trashing periodically or spend a cheap, spare buy (e.g. Princess lets me grab a Amulet for $1 & a buy) and kill the curses in turn. Once your deck is maximally thinned, lining up trash and trasher is really easy and 8 debt becomes a much higher opportunity cost. Plus, of course, there are plenty of options for gaining trashing on the cheap - Iw a Smerch to deal with Kc/Nbrig. $8 with a buy is almost always enough to buy 2 out of the three things you need to trash in turn - draw, action, and trashing ability; very often you will already have one of those in excess.
Some might argue that getting junking attacks in a Donate game is bad, but ultimately if I spend $5 on something like Mountebank or Witch, I am forcing you to spend $8 later. Not always a good trade with future discounting, but not always bad if I want the secondary bonus of the attack (e.g. if I need net draw for my Tr engine).
2. In like manner I may be gaining junk (e.g. Followers, Defiled shrine, Ritual, Whunt, Gkeeper) for some benefit and the opportunity cost of adding a trasher is less than Donating periodically. Other similar ideas include cheap Possession defense (trash out some coin so my deck no longer hit $8 without having to skip a Possession buy). Repeated activation of on-trash cards (e.g. Sqr, Feoda).
3. Deck tailoring for scoring Landmarks on the final turn. For example I might grab a Chapel so I have the option of dumping Gold with Bandit Fort if I think I can three pile soon. Likewise, I may want to get rid of stuff like trashing attacks or duration cards with Wall out (e.g. Tr/Chapel on my last turn to burn Amb/Opost/3x Hwoods/3x village for a net gain of 7 VP). Wolf den is also possible. I could donate my penultimate turn ... but that means my opponent has a turn to respond and I have to burn a $8 and a buy.
4. Seeding on gain bonuses (e.g. Bv, Mandarin, Inn) into the trash during my turn to gain them with Grobber or Rogue. This prevents my opponent from snagging my bonuses.