Some casinos forbid using betting patterns in their Terms and Conditions (T&Cs). If a player is discovered to be using forbidden betting patterns, casinos often decline their withdrawals and confiscate their winnings.
Casinos use this rule to protect themselves against bonus abusers, who can often be identified by their betting patterns. However, some casinos also apply this rule to regular players and use it as an excuse to decline withdrawals of legitimate winnings.
Theoretically, any sequence of bets can be called a betting pattern. If the casino wishes to forbid the use of certain betting patterns, these should at least be specified in detail so that players know exactly what they can and cannot do. Otherwise, the 'betting patterns' rule could be used against everybody.
So casinos shouldn't use betting patterns as an excuse not to pay out winnings to players. These betting patterns can indeed be a sign that a player is doing something against the rules, but they shouldn't be the sole reason to penalize players.