Should companies who sell products that are known to cause harm to people that consume them be allowed to continue to keep doing so? Is the quest for profits really more important than the harm they cause to others?

Harm is too subjective.
People should be responsible for themselves.

Given those two statements I must say NO to your question.

In reference to those companies that produce and sell alcohol and tobacco:

Here is a direct quote from a site listing the most harmful drugs:

http://www.drbenkim.com/ten-most-dangerous-drugs.html

"Ranked from most to least dangerous, the ten most dangerous substances were deemed to be:

1. Heroin - popular street names include smack, skag, and junk.
2. Cocaine - often referred to as snow, flake, coke, and blow.
3. Barbiturates - popular slang names include yellow jackets, reds, blues, Amy's, and rainbows.
4. Street Methadone
5. Alcohol
6. Ketamine - a powerful hallucinogen, often referred to as Special K.
7. Benzodiazepines - a family of sedative drugs.
8. Amphetamines - known as greenies among baseball players.
9. Tobacco
10. Buprenorphine - also called bupe or subbies.

The remaining drugs that were assessed in this study ranked as follows:

1. Cannabis - includes marijuana.
2. Solvents - volatile substances that can be inhaled, such as glue, nail polish remover, paints, hair spray, and lighter fuel (gas).
3. 4-MTA - is a derivative of amphetamine and has similar effects to ecstasy.
4. LSD
5. Methylphenidate - central nervous system stimulant, commonly sold as ritalin.
6. Anabolic steroids
7. GHB - short for Gamma hydroxybutyrate, a powerful central nervous system depressant, most commonly known as the date rape drug.
8. Ecstasy
9. Alkyl nitrates - group of drugs commonly referred to as poppers.
10. Khat - an amphetamine-like stimulant.

It is estimated that tobacco causes 40 percent of all hospital illnesses, while alcohol is involved in more than 50 percent of all visits to hospital emergency rooms. In light of these statistics, the authors of this study question why alcohol and tobacco are legal to use within current drug policies for Britain and the United States, while less harmful drugs like ecstasy and LSD are deemed illegal to use.

The bottom line: alcohol and tobacco are two of the most dangerous substances that you can expose yourself to on a regular basis. In terms of overall potential to cause harm, if used regularly, alcohol and tobacco belong in the same category as other recreational drugs like cocaine and heroin."

Given this information, how can we possibly allow them to continue to legally sell products that are more harmful than those other, less harmful yet illegal, products?