Water and sewer often fall into this category, and inside the City of Phila unpaid natural gas turns into a lien. 

They are initially attractive and more cost effective that natural slate but not necessary a better value in all cases.

If the only issue is the odor, I would use Simple Solution or Nature's Miracle, both found at Pet Smart.  

If I were purchasing a house to live in or rent, I would favor natural brick or natural stone or wood or hardy plank.

Same thing goes for people who are extremely lazy by nature, and are not willing to endure any effort or sacrifice to maximize their product's potential.Conversely, big ego people, ones that think they, and everything they touch, is gold, often set rates far higher than they can reasonably get - and then raise hell about the tenant pool, other landlords, tax cuts, and everything else under the sun when the unit sits there vacant, forever.

Just the nature of the business.

The key here is that the sales contract is not personal to the buyer under its terms or by its nature; if it is, then there can be no assignment by the purchaser.As explained by the Florida Supreme Court, real estate buyers will be allowed to assign (sell) their contracts to someone else whenever they choose to do so — unless (1) there is language in the contract that prohibits it in that particular deal; (2) if the assignment would violate public policy in some way; or (3) if it would violate some state or federal law or statute.One other possible limitation on assigning a real estate sales contract (assuming the contract is silent on the issue of it being assignable): it may not be assigned if the seller has agreed to sell to this particular buyer because of an explicit reliance upon that buyer’s personal credit to cover the transaction.

Death in a property really freaks people out, even from natural causes.

I think it's a natural part of the real estate cycle.

@John Thedford that may be true dependent on the specific circumstance, but buy and hold properties have a disadvantage in the short term because profits are deferred and are by nature not as liquid as straight cash immediately